IC-NRLF 


SB    27    073 


pen  Heart 
Steel  Castin 


W.M.CABR 


LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


Class 


OPEN    HEARTH 
STEEL    CASTINGS 


BY  W.  M.  CARR 

4  « 


A  complete  exposition  of  the  methods  involved  in  the 
manufacture  of  open-hearth  steel  castings  by  the  basic  and 
acid  processes.  This  work  is  compiled  from  a  series  of 
articles  by  the  author,  written  for  and  published  by  The 
Iron  Trade  Revieiv  and  The  Foundry. 


UNIVERSITY 

OF 


Cleveland,  Ohio,  U.  S.  A. 

The  Penton  Publishing  Company,  Publishers. 

ipo; 


:AL 
TABLE  OF  CONTENTS 


CHAPTER   I. 

Page 
Melting  Stock  for  Acid  Practice  .............................      8 

Fuels   and  Alloys  .............................................     10 

Molding    Materials  ..................  .  ........................     13 

Materials  for  Basic  Practice  ..................................     14 

CHAPTER   II. 

Open-Hearth   Furnace   Construction  ...........................     20 

CHAPTER   III. 

Fuels  and  Accessories  ...........  .............................     33 

CHAPTER  IV. 

Manipulation  of  Heats  in  Acid  Practice  .......................     40 

CHAPTER  V. 

Manipulation  of  Heats  in  Basic  Practice  ...................... 

Order   of   Charging  ........................................... 

Melting    .....................................................     60 

Charging    Cold    Stock  ........................................     61 

CHAPTER  VI. 

Chemical  Analyses  and  Physical  Tests  ........................     ?2 


CHAPTER  VII. 

Relation  Between  Composition  and  Physical  Properties  ........     81 


CHAPTER  VIII. 

Blow   Holes   in    Steel   Castings 94 

CHAPTER   IX. 

Discussion  of  the  Causes  of  Cracks  in  Steel  Castings 98 

CHAPTER   X. 

Heat  Treatment  and  Annealing 101 

CHAPTER   XI. 

Repair  of  Steel  Castings  with  Thermit Ill 

CHAPTER  XII. 

Cost  of  Equipment  for  Open-Hearth  Steel  Foundries..  .  115 


1.61533 


ILLUSTRATIONS 


Page 

Plan  view,  stationary  type  open-hearth  furnace 21 

Sectional  elevation,  open-hearth  furnace 22 

Cross  section,   open-hearth   furnace 23 

Gas    Producer    34 

Oil  Burner  for  open-hearth  furnace 36 

Open-hearth  furnace,  arranged  for  burning  oil 37 

Diagram  of  variations  in  composition  of  a  normal  acid  open- 
hearth  heat   42 

Diagram  of  variations  in  composition  of  a  normal  basic  open- 
hearth  heat   66 

Standard  Test  Bar    78 

Test  Bar  for  Works'  test  79 

Shrink   hole    95 

Blow  Holes  caused  by  gaseous  steel  imperfectly  deoxidized....     96 

Blow  Holes  caused  by  damp  sand  96 

Diagram  of  structural  changes   103 

Record  of  Government  Tests    106 

Specimen  of  cast  steel  as  cast1 108 

Specimen  of  cast  steel  heated  to  1,200  Degrees  Cent 108 

Specimen    of    cast    steel    heated   to    1,200    Degrees    Cent,    air 

quenched    109 

Specimen  of  cast  steel  heated  to  800  Degrees  Cent 109 


«pB*tAj^ 

OF  THE     ^ 

UNIVERSITY 

OF 


CHAPTER  I 

MELTING  STOCK  FOR  ACID  AND  BASIC  PRACTICE — REFRAC- 
TORIES— FUELS — ALLOYS — MOLDING   MATERIALS 
FLUXES 

In  view  of  the  growing  interest  manifested  by  both  pro- 
ducers and  consumers  of  cast  sections  in  the  production  of 
steel  castings  and  their  increasing  utility,  the  salient  points 
of  their  manufacture  by  the  acid  basic  and  open-hearth 
processes  will  be  presented  in  this  series  of  articles  which 
cover : 

First — The  selection  and  representative  composition  of 
melting  stocks,  alloys,  refractories,  fuels,  melting  materials 
and  fluxes. 

Second — Furnace  construction  and  the  melting  and  ma- 
nipulation of  heats. 

Third — The  conditions  of  melting  as  effecting  the  physi- 
cal properties  of  products. 

Fourth — The  analyses  and  physical  tests  of  different 
grades  of  products. 

Fifth — The  effect  of  the  constituent  materials  and  metal- 
loids usually  present  in  open-hearth  steel  castings. 

Sixth — Heat  treatment  or  annealing,  with  notes  on  micro- 
scopic examinations. 

Seventh — Discussion  of  the  causes  of  blow  holes  and 
shrinkage  cracks. 

Eighth — The  repair  of  defects  by  thermit  welding. 

Ninth — Approximate   cost   of   open-hearth   installations. 


8  MELTING  STOCK  FOR  ACID  PRACTICE 


MATERIALS    FOR    ACID    PRACTICE 

MELTING  STOCK. — The  composition  of  materials  for  acid 
castings  comes  within  well  defined  limits,  for  the  main  rea- 
son that  the  process  is  nearer  a  melting,  rather  than  a  re- 
fining one,  owing  to  the  fact  that  the  metalloids,  sulphur 
and  phosphorus,  are  not  removed  during  the  conversion  of 
the  charge.  As  their  presence  in  the  finished  product  must 
be  subject  to  specification,  it  follows  that  the  melting  stock 
must  be  bought  with  a  limit  to  the  contents  of  the  elements 
named.  Only  in  regard  to  quantities  of  sulphur  and  phos- 
phorus exists  the  distinction  between  acid  and  basic  melt- 
ing stock.  Pig  iron  for  ordinary  practice  analyzes  as  fol- 
lows :  , 

Total  Carbon   2-3.5  per  cent 

Silicon    0.50-1.5  per  cent 

Sulphur  0.04  or  less 

Phosphorus 0.04  or  less 

Manganese   0.50-0.75 

In  addition  to  pig  iron,  steel  scrap  known  as  "basic  scrap" 
is  also  bought  on  analysis  or  chemical  specifications.  Being 
the  product  of  rolling  mills,  etc.,  following  basic  practice, 
the  contents  of  sulphur  and  phosphorus  are  usually  low, 
and  they  are  the  only  elements  of  composition  taken  into  ac- 
count. A  representative  analysis  of  steel  scrap  for  acid 
practice  is  as  follows: 

Sulphur   0.015-0.03  per  cent 

Phosphorus  0.010-0.03  per  cent 

Since  the  physical  character  is  usually  represented  by 
billets,  crop  ends,  blooms,  plate-shearings,  defective  castings 
and  waste  metal  from  steel  foundries,  the  nature  of  them 
necessarily  predetermines  the  composition  in  regard  to  the 
presence  of  carbon,  silicon  and  manganese.  With  a  charge 
of  pig  iron  and  steel  scrap  it  is  comparatively  easy  to  keep 


REFRACTORIES  FOR  ACID  OPEN   HEARTH   FURNACES 


the  composition  of  finished  product  within  acid  specifica- 
tions. 

REFRACTORIES 

Silica  sand  forming  the  hearth  of  the  furnace,  known 
chemically  as  an  acid,  lends  its  classification  to  distinguish 
between  the  two  processes.  It  does  not  present  a  condition 
wherein  certain  elements  are  removed  during  melting  of 
stock,  namely,  sulphur  and  phosphorus.  The  amounts  of 
those  elements  charged  will  be  found  in  the  finished  product. 
The  function  of  silica  sand  is  mainly  a  refractory  one. 
That  is,  it  must  have  heat  resisting  qualities,  but  not  to  the 
extent  that  it  will  not  set  or  sinter  slightly  to  satisfactorily 
preserve  the  contour  of  the  shallow  dish-like  formation  of 
the  hearth.  It  must  not  be  too  fusible,  otherwise  there 
would  be  excessive  scorification  or  cutting  of  the  hearth.  It 
must  set  or  sinter  sufficiently  to  resist  abrasion  due  to  the 
charging  of  stock.  It  is  difficult  to  lay  down  strict  chemical 
specifications  for  silica  sand.  There  are  certain  conditions 
of  composition  not  expressed  by  an  analysis  of  the  total 
constituents.  The  combinations  of  them  with  their  neigh- 
bors cannot  be  ascertained.  However,  a  silica  sand  of  the 
following  analysis  gave  excellent  results  in  practice: 

Water   0.24  per  cent 

Silica    97-25  per  cent 

Alumina  and  Iron   Oxide 0.16  per  cent 

Lime    0.08  per  cent 

Magnesia   0.39  per  cent 

Alkalies    0.36  per  cent 

Loss  on  Ignition  0.36  per  cent 

There  are  several  deposits  of  silica  sand  in  the  west  and 
middle  west  that  are  supplied  to  steel  foundries  and  no 
difficulty  will  be  found  in  getting  the  best  quality  for  the 
purpose.  As  a  general  rule  a  silica  sand  for  hearth  lining 
must  be  low  in  lime,  manganese  and  the  alkalies  (potash 


IO  FUELS  AND  ALLOYS 


and  soda)  ;  an  excess  of  any  tends  to  lower  the  fusion  point 
of  the  sand,  destroying  its  required  sintering  or  refractori- 
ness. Usually  a  silica  sand  with  less  than  95  per  cent  silica 
will  not  answer  for  a  refractory. 


FUEL 


It  is  a  question  of  local  conditions  as  to  whether  the  fuel 
may  be  natural  gas,  oil,  tar,  or  producer  gas.  Natural  gas 
is  by  far  the  most  satisfactory,  owing  to  its  high  calorific 
value  and  its  non-contamination  of  the  bath  or  molten 
charge.  It  is  fed  directly  into  the  working  body  of  the  fur- 
nace without  any  preheating  or  a  passing  through  the  re- 
generator chambers.  Oil,  next  in  efficiency,  may  be  crude 
petroleum  or  a  grade  known  as  residuum ;  a  by-product  of 
petroleum  distillation.  The  heating  values  are  high,  and 
in  certain  grades  the  composition  will  answer  for  acid  work. 
Some  grades  are  rather  high  in  sulphur,  which  is  absorbed 
by  the  stock  in  melting. 

Tar  has  been  satisfactorily  used  when  available  as  a  by- 
product in  the  manufacture  of  coke  by  Otto-Hoffman  re- 
tort ovens.  The  construction  of  burners  permitted  a  sim- 
ultaneous burning  of  the  gas  resulting  from  the  coke  retorts. 

Producer  gas  is  used  extensively  and  when  near  a  reliable 
supply  of  coal,  is  considered  cheaper  than  the  aforemen- 
tioned fuels.  A  description  of  gas  producers  and  liquid 
fuel  burners  will  be  given  in  subsequent  chapters.  Gas  dis- 
tilled in  a  producer  does  not  have  as  high  a  heating  value 
as  liquid  fuels,  nor  is  the  efficiency  so  great,  because  many 
of  the  total  heat  units  are  lost  in  the  process  of  distillation 
of  the  coal  (soft  or  anthracite).  With  liquid  fuels  or  natu- 
ral gas  the  total  thermal  efficiency  is  available  within  the 
working  body  of  the  furnace,  there  being  no  in- 
termediate losses  before  delivery  at  the  point  of  com- 
bustion. Natural  gas  or  liquid  fuels  are  easy  of  control  in 
flame  regulation ;  furnace  construction  and  repairs  are  sim- 
plified and  lessened ;  regularity  of  product  and  longer  cam- 


FUELS  AND  ALLOYS  1 1 

paigns  are  assured.  Producer  gas  is  irregular,  and  owing 
to  heavy  deposits  of  tarry  and  sooty  matter,  regular  weekly 
stoppages  must  be  made  to  clean  out  mains  and  flues. 
Liquid  fuels  or  natural  gas  eliminate  such  losses  of  working 
time. 

HEATING  VALUE  OF  FUELS 
B.    T.    U. 


Natural  Gas  300-600  per  cubic  foot 

Oil    14000-17000  per  pound 

Tar  15000      per  pound 

Producer  Gas  100-150  per  cubic  foot 

Bituminous  Coal  10000-12500  per  pound 

One  ton  of  bituminous  coal  yields  in  a  modern  producer, 
160,000  cubic  feet  of  gas  with  65  per  cent  efficiency  in 
heating  value  of  the  coal. 


ALLOYS 

FERRO-MANGANESE. — The  standard  quality  contains  80 
per  cent  manganese.  A  representative  analysis  will  be  as 
follows : 


Iron  12.14    per  cent 

Manganese  80.00    per  cent 

Carbon    ; .  5.6    per  cent 

Silicon   0.5    -i.oo  per  cent 

Sulphur    0.010-0.03  per  cent 

Phosphorus  0.100-0.75  per  cent 


FERRO- SILICON.— The  standard  grade  carries  13  per  cent 
silicon  and  is  usually  sold  on  a  guarantee  of  n  per  cent  of 
that  element.  The  following  is  a  usual  analysis: 


12  FUELS  AND  ALLOYS 


Silicon   9  13  per  cent 

Carbon  i     2  per  cent 

Sulphur  0.04-0.08  per  cent 

Phosphorus    0.10-0.50  per  cent 


In  recent  years  there  have  been  put  on  the  market  sev- 
eral grades  of  electrolytic  silicons  that  are  very  satisfactory. 
The  most  economical  grade  is  the  one  carrying  50  per  cent 
silicon,  and  considered  on  the  basis  of  the  unit  cost  of  sili- 
con, is  cheaper  than  the  commoner  alloy.  The  following  is 
a  typical  composition  of  an  electric  furnace  f erro-silicon : 


Silicon   50  52  per  cent 

Iron    44  46  per  cent 

Carbon    0.15  -0.25  per  cent 

Sulphur    0.003-0.010  per  cent 

Phosphorus    0.04  -0.06  per  cent 


The  purpose  of  the  aforementioned  alloys  will  be  con- 
sidered farther  on. 

IRON  ORE. — The  purpose  of  iron  ore  is  two-fold.  One  is 
to  increase  the  fluidity  of  plastic  slags,  the  other  as  a  car- 
rier of  oxygen  to  assist  in  the  removal  of  the  carbon  from 
the  bath  of  molten  metal.  The  total  iron  liberated  in  the  in- 
terchange between  its  oxygen  and  the  carbon  of  the  bath 
adds  to  the  yield  of  metal.  The  most  satisfactory  ores  for 
open-hearth  practice  are  the  magnetites  or  hard  hematites. 
The  soft  ores  are  apt  to  dissipate  their  combined  usefulness 
in  the  slag  instead  of  oxidizing  carbon.  No  particular 
limits  are  placed  on  their  compositions,  excepting  that  they 
be  high  in  iron  and  moderately  low  in  phosphorus.  A  fair 
analysis  is  as  follows: 


Iron   60  68      per  cent 

Silica    15        per  cent 

Sulphur   0.05-0.100  per  cent 

Phosphorus    0.03-0.500  per  cent 


MOLDING   MATERIALS  13 


MOLDING  MATERIALS. — Since  all  steel  castings  are  poured 
at  higher  ranges  of  temperature  than  gray  iron  or  malleable 
castings,  it  is  essential  that  the  sands  and  clays  (binders) 
be  as  refractory  as  possible.  Pure  silica  is  the  most  de- 
sirable— the  purer  the  better.  The  following  is  an  analysis 
of  a  typical  steel  molding  sand : 


Silica  98.  5  per  cent 

Alumina   1.40  per  cent 

Iron  Oxide 0.06  per  cent 

Lime    0.20  per  cent 

Magnesia   0.16  per  cent 

Combined  Water  0.14  per  cent 

Alkalies 0.25  per  cent 


It  must  be  of  such  a  nature  or  structure  physically  that 
the  heated  gases  in  the  mold  when  displaced  by  liquid  steel 
will  have  a  free  passage  outwardly.  It  is  preferable  that  the 
grains  be  sharp  and  irregular  rather  than  rounded  as  would 
be  the  case  with  sand  subjected  at  some  time  to  the  action 
of  water.  The  color  is  often  white  or  slightly  tinged  with 
yellow.  Its  color  is  not  necessarily  a  guide  to  its  qualities, 
but  it  is  often  an  indication. 

FIRE  CLAY. — Pure  Silica  sand  having  no  binding  proper- 
ties, varying  amounts  of  clay  are  mixed  with  it  to  give  the 
sand  a  needed  bond  and  substantiality  to  the  mold  prepared 
for  the  reception  of  the  hot  steel.  The  clay  must  also  be 
refractory  and  possess  a  maximum  degree  of  plasticity. 
Low  grade  sands  and  clays  would  fuse  at  the  temperature 
of  liquid  steel  and  cause  the  castings  to  be  of  an  irregular 
rough  surface.  An  attempt  to  economize  in  the  sand  pile 
is  apt  to  spoil  one's  reputation  for  clean-looking  castings. 

It  is  not  always  reliable  to  have  recourse  to  chemical  tests 
on  refractories  or  molding  materials,  since  actual  practice 
will  affirm  the  desirable  qualities  in  them.  The  following  is 
a  typical  composition  of  fire  clay : 


14  MELTING   STOCK   FOR   BASIC   PRACTICE 


Silica    60  66      per  cent 

Alumina    25  20      per  cent 

Iron  Oxide  nil-  2.00  per  cent 

Lime   nil-  i.oo  per  cent 

Magnesia  nil-  i.oo  per  cent 

Alakalies    .- nil-  2.00  per  cent 

Combined   Water    7.50-10.50  per  cent 

The  value  of  a  fire  clay  depends  largely  upon  a  low  con- 
tent of  alkalies  and  a  freedom  from  carbonates  of  lime. 
Oxide  of  iron  has  a  strong  fluxing  effect,  but  its  presence 
below  3  per  cent  is  harmless. 

CORE  COMPOUNDS. — Any  reliable  proprietary  article  will 
answer  and  the  list  will  include  molasses  water,  rosin,  flour, 
linseed  oil,  etc.,  all  of  which  are  too  well  known  to  need 
any  description. 


MATERIALS    FOR   BASIC    PRACTICE 

MELTING  STOCK. — Basic  melting  possesses  a  marred  flex- 
ibility in  the  selection  of  stock  over  acid  melting.  It  is  by 
some  considered  a  sort  of  metallurgical  scavenger.  While 
it  is  true  that  there  are  greater  latitudes  in  quality  of  pig 
iron  and  scrap  yet  it  must  not  be  overlooked  that  the  pro- 
miscuous dumping  of  any  kind  of  stock  into  a  basic  furnace 
cannot  yield  a  reliable  product.  If  good  castings  are  the 
object  sought,  discretion  must  be  observed  in  the  selection 
of  materials  entering  into  their  manufacture.  In  regard 
to  quantity  basic  pig  iron  greatly  exceeds  acid  pig  so  far  as 
availability  is  concerned.  The  ores  of  the  southern  and 
south-western  states  are  plentifully  endowed  by  nature  for 
the  yield  of  unlimited  supplies  of  basic  pig.  As  to  scrap, 
the  situation  is  somewhat  of  an  uncertainty,  owing  to  the 
inroads  made  by  the  larger  interests  engaged  in  the  produc- 
tion of  ingots  in  basic  bottoms.  In  consequence  prices  for 
scrap  have  a  tendency  to  gradually  rise.  The  factors  con- 
trolling the  choice  between  basic  and  acid  practice  for  cast- 
ings are  ones  of  location  and  continguity  to  the  sources  of 


MELTING   STOCK   FOR   BASIC    PRACTICE  15 


supply  of  raw  materials.  So  far  as  the  relative  value  of  the 
product  of  either  process  is  concerned,  it  is  true  that  basic 
castings  are  fully  as  satisfactory,  from  the  view  point  of 
quality,  as  those  made  by  the  acid  process.  It  must  be  re- 
membered, one  is  a  melting  method  and  the  other  a  refining 
one.  The  basic  process  to  get  good  results  needs  intelli- 
gent handling  and  a  higher  development  of  melting  skill. 
The  pig  iron  necessary  is  known  as  "standard  basic"  and 
the  following  analysis  represents  the  ulterior  limits  in  com- 
position : 

Silicon  i.oo  per  cent 

Sulphur    0.05  per  cent 

Phosphorus   i.oo  per  cent 

"Off-basic"  can  carry  as  high  as  1.50  silicon  and  again 
as  high  as  0.07  sulphur.  Shipments  of  these  grades  on 
standard  contracts  can  be  accepted  at  a  concession  in  price 
and  it  is  permissible  to  use  a  moderate  amount  of  "off- 
basic"  in  charges  with  no  harm  to  follow.  As  was  men- 
tioned under  "Acid  Melting  Stock"  the  sulphur  and  phos- 
phorus charged  in  that  process  would  equal  that  of  the  fin- 
ished product.  In  basic  melting  it  is  possible  to  eliminate 
50  to  75  per  cent  of  the  sulphur  and  95  per  cent  of  the 
phosphorus,  thanks  to  the  character  of  the  lining  of  the  fur- 
nace and  slags  formed  by  the  liberal  additions  of 
limestone  with  the  charge.  For  castings  it  is  de- 
sirable to  have  on  hand  several  brands  of  basic  pig; 
some  with  low  phosphorus  and  some  with  high  manganese. 
Certain  brands  can  be  obtained  with  phosphorus  as  low  as 
O;2OO  while  standard  in  other  particulars  and  at  ruling 
prices.  Brands  with  high  manganese  ranging  from  1.5  to 
3.00  per  cent  command  a  higher  price.  It  is  not  good  prac- 
tice to  make  the  entire  pig  iron  charge  high  phosphorus 
stock.  The  reasons  for  mixing  brands  in  regard  to  phos- 
phorus and  manganese  will  be  considered  under  furnace 
manipulation. 

STEEL  SCRAP. — The  character  of  this  material  is  not  con- 


1 6  REFRACTORIES   FOR   BASIC   FURNACES 


sidered  chemically  because  the  physical  nature  of  it  brings 
it  well  within  working  limits  as  to  composition.  It  is  usu- 
ally designated  "heavy  railroad  melting  scrap,"  but  liber- 
ties are  sometimes  taken  and  unless  the  consumer  exer- 
cises circumspection  almost  anything  may  be  found  in  it 
from  shop  sweepings  to  tomato  cans.  Heavy  scrap  is  the 
desideratum,  and  may  consist  of,  as  an  illustration,  steel 
rails,  knuckles,  draw  bars,  wheel  centers,  car-springs,  fish- 
plates, defective  castings  (steel),  ingots,  etc.  Gray  iron 
castings  should  be  religiously  excluded  when  sold  as  steel 
scrap.  It  is  allowable  to  use  limited  quantities  of  defective 
malleable  castings  although  draw  bars  of  such  materials  are 
sold  as  steel.  Five  per  cent  of  the  scrap  charge  in  malleable 
scrap  will  not  upset  the  melter's  calculations.  The  scrap 
charge  will  be  augmented  by  daily  waste  from  the  foundry. 

REFRACTORIES 

The  hearth  of  basic  furnaces  in  American  practice  is 
made  writh  magnesite,  a  substance  classified  chemically  as  a 
base  and  possessing  the  quality,  in  addition  to  resisting 
high  temperatures,  of  being  but  slightly  affected  by  a  slag 
highly  charged  with  lime  which  would  be  fatal  to  a  hearth 
lined  with  silica  sand.  To  lengthen  the  life  and  efficiency 
of  a  basic  hearth  the  first  consideration  is  to  keep  out  of  the 
charge  as  much  silicious  matter  as  possible.  Magnesite, 
the  carbonate  of  magnesia,  is  an  importation  from  Austria, 
where  it  is  calcined  converting  it  into  magnesia,  the  oxide  of 
the  metal  magnesium,  by  the  removal  of  the  major  portion 
of  carbon  dioxide.  It  is  still  considered  commercially  as  a 
magnesite.  Its  composition  ranges  as  follows: 


RAW 

Magnesium   Carbonate    93-!9  Per  cent 

Calcium  Carbonate    1-43  per  cent 

Iron   Carbonate    2.61  per  cent 

Silica  2.75  per  cent 


REFRACTORIES   FOR  BASIC   FURNACES  17 


CALCINED 

Magnesia  90  95        per  cent 

Lime  i    2        per  cent 

Iron  Oxide   0.5-3.50  per  cent 

Silica  0.5-2.75  per  cent 

Volatile  Matter  0.5-1.00  per  cent 

DOLOMITE. — This  material  is  extensively  deposited  in  the 
United  States.  It  is  a  double  carbonate  of  lime  and  mag- 
nesia. It  is  used  either  calcined  or  raw.  Principally  it  is 
used  for  patching  slag  lines,  where  scorification  of  the 
hearth  is  the  heaviest.  It  is  not  recommended  for  points 
below  the  slag  line.  A  typical  analysis  is  as  follows : 


RAW 

Silica   0.5  2.00  per  cen* 

Iron    Oxide    0.5  2.00  per  cent 

Alumina    0.5  2.00  per  cent 

Calcium    Carbonate    50     55  per  cent 

Magnesium   ' 40     44  per  cent 


CALCINED 

Silica    0.5  2.00  per  cent 

Iron   Oxide    0.5  2.00  per  cent 

Alumina    0.5  2.00  per  cent 

Lime 50     55  per  cent 

Magnesia   37     45  per  cent 

CHROME  ORE. — A  substance  highly  refractory  to  heat 
and  neutral  to  the  action  of  acid  and  basic  slags.  Unfortu- 
nately it  has  no  bond  and  for  that  reason  its  uses  are  some- 
what limited.  It  is  used  for  patching  parts  of  the  hearth 
where  cutting  above  the  slag  line  is  severe  upon  the  brick 
work,  usually  in  gas  ports  and  door  jambs.  (In  European 
practice  it  is  stated  that  entire  hearths  are  lined  with  lump 


1 8  REFRACTORIES  FOR  BASIC  FURNACES 


chrome  ore.)  Aside  from  patching  it  is  used  as  a  neutral 
lining  between  magnesite  and  silica  bricks.  Its  composi- 
tion is  as  follows: 


Chromic  Oxide   40-60  per  cent 

Iron    15-18  per  cent 

Alumina    5-30  per  cent 

Silica    1-5    per  cent 


FLUXES 

The  most  efficient  in  basic  melting-  is  ordinary  limestone. 
Its  function  is  to  form  a  slag  that  will  readily  absorb  the 
sulphur  and  phosphorus  of  the  charge  and  act  as  a  vehicle 
for  the  oxidizable  silicon,  iron  and  manganese.  The  purer 
the  grade  the  better,  that  is,  a  richness  in  carbonate  of  lime 
and  a  freedom  from  silica. 

A  fair  analysis  is  as  follows: 


Silica    0.25-  i.oo  per  cent 

Oxide  of  Iron  and  Alumina 0.50-  2.00  per  cent 

Carbonate  of  Lime    95.     -99.      per  cent 

Carbonate  of  Magnesia   0.5  -  i.oo  per  cent 

FLUORSPAR. — The  function  of  this  material  is  to  thin  a 
limey  slag  when  in  the  judgment  of  the  melter  it  seems 
thick  or  sluggish.  A  moderate  addition  of  fluorspar  will 
liven  it  and  its  action  may  be  likened  to  certain  fluxes  used 
in  brazing  metals — the  property  of  dissolving  at  higher 
temperatures  metallic  oxides.  It  is  plentifully  deposited  in 
the  United  States.  A  good  grade  will  analyze  as  follows: 

Calcium   Fluoride    90-98       per  cent 

Oxide  of  Iron  and  Alumina  0.5-1.00  per  cent 

Silica    nil-i.oo  per  cent 

IRON  ORE. — See  "Acid  Melting  Materials." 


FLUXES   FOR   BASIC   PRACTICE 


ALLOYS.— See  "Acid  Melting  Materials." 

FUELS. — See  "Acid  Melting  Materials." 

As  a  guide  to  purchasing  stock  the  following  tabulations 
will  be  of  assistance  in  furnishing  approximate  amounts 
for  regular  consumption.  The  figures  are  based  on  the 
different  kinds  of  stock  necessary  to  produce  I  net  ton  of 
castings : 


Acid.  Basic. 

Pig  Iron  620  pounds  1227  pounds 

Steel  Scrap    1880  pounds  1227  pounds 

Ferro-Silicon 54  pounds  57  pounds 

Ferro-Manganese 28  pounds  35  pounds 

Iron   Ore    26  pounds  30  pounds 

Aluminum  3-10  pounds  3-10  pounds 

Limestone    300  pounds 

Magnesite 34  pounds 

Silica  Sand   1800  pounds  1600  pounds 

Fire  Clay  300  oounds  350  pounds 

Gas   Coal   950  pounds  1250  pounds 

Fuel  Oil 55    gallons  80  pounds 

Boiler  Coal  (power)   900  pounds  900  pounds 


CHAPTER  II 


FURNACE    CONSTRUCTION — AREAS    AND    VOLUME — DRAFT 
REGENERATION 


In  American  practice,  when  larger  tonnages  in  output 
are  sought,  the  general  capacity  of  an  open-hearth  furnace 
working  on  castings  is  about  20  tons  per  heat.  This  ca- 
pacity approaches  the  maximum  that  can  be  economically 
handled  in  jobbing  shops  and  will  amply  represent  a  gen- 
eral rule.  Larger  tonnages  may  be  occasionally  needed  if 
the  class  of  product  is  in  the  shape  of  heavy  work  requiring 
but  a  few  molds  to  receive  a  heat  of  steel  and  consuming 
but  a  moderate  interval  of  time  to  pour  them,  but  in  cases 
of  a  heat  of  steel  to  be  put  into  a  large  number  of  molds 
the  pouring  time  may  be  so  extended  that  the  metal  will 
lose  its  temperature.  Therefore,  charges  exceeding  20  tons 
for  miscellaneous  castings  are  apt  to  result  in  losses  due  to 
cold  steel.  The  illustrations,  Figs,  i,  2  and  3,  given  here- 
with, show  the  usual  lines  of  a  modern  stationary  furnace 
of  20  tons  capacity.  The  lines  are  the  ultimate  of  experi- 
ence in  various  plants  and  embody  the  best  that  is  obtain- 
able for  that  type  of  furnace  at  the  present  time.  As  they 
»re  only  representative  they  may  be  subject  to  some  minor 
changes  which  may  be  dictated  by  necessities  arising  from 
local  conditions  in  erecting.  The  principles  of  construction 
are  the  same  in  both  acid  and  basic  furnaces,  the  differences 
occurring  in  the  character  of  the  materials  forming  the 


OF  THt 

UNIVERSITY 

OF 
^ 

OPEN-HEARTH    FURNACE   CONSTRUCTION 


21 


hearth  linings.  Generally  the  furnaces  are  of  the  stationary 
type.  In  some  plants  will  be  found  furnaces  of  the  rolling 
or  tilting  kinds,  each  having  some  good  points  in  its  favor. 
From  the  viewpoint  of  cheapness  of  construction  the  sta- 
tionary furnace  holds  the  ground.  Movable  hearth  types 
call  for  costly  mechanical  installation  not  required  in  sta- 
tionary units.  A  potent  argument  in  favor  of  the  movable 


FIG.    1. — PLAN     VIEW,     STATIONARY    TYPE     OPEN-HEARTH     STEEL 
MELTING  FURNACE. 


(rolling  or  tilting)  furnace  is  the  ability  offered  to  com- 
pletely drain  the  hearth  at  the  end  of  a  melt  thus  emptying 
any  pools  that  may  form  in  the  bottom  due  to  excessive 
scorification  and  the  ease  with  which  they  can  be  readily 
repaired  with  proper  refractories.  In  stationary  furnaces 
much  time  is  lost,  with  much  discomfort  to  the  workmen  in 
emptying  pools  or  "puddles"  by  means  of  rabbles  or  scrap- 
ers. They  cannot  be  thoroughly  drained  by  such  means 
and  the  subsequent  patching  may  or  may  not  be  satisfac- 


22 


OPEN-HEARTH    FURNACE    CONSTRUCTION 


torily  accomplished.  The  patching  may  become  loosened 
in  a  succeeding  melt.  Such  difficulties  are  more  liable  to 
happen  in  basic  bottoms  than  on  acid.  Another  argument  in 
favor  of  the  movable  furnaces  is  that  the  tapping  hole 
troubles  are  eliminated.  In  stationary  furnaces  difficulties 
and  annoying  delays  are  encountered  through  "hard-taps" 
as  a  result  of  the  materials  used  to  temporarily  close  the 
tapping  hole  becoming  fused  or  hardened  and  offering 
great  resistance  to  tools  necessary  to  open  it  at  the  proper 
time.  In  well  ordered  plants  such  difficulties  are  a  rare  oc- 
currence, but  still  the  risk  exists.  With  a  movable  furnace 
the  tapping  hole  is  never  tamped  or  closed  so  that  there  is 


FIG.  2. — SECTIONAL,  STATIONARY  TYPE  OPEN-HEARTH   STEEL 
MELTING  FURNACE 


always  the  assurance  that  the  metal  can  be  drawn  off  when 
desired.  Against  these  favorable  considerations  is  the  com- 
paratively heavier  .first  cost  of  the  movable  furnaces  over 
the  stationary,  so  that  the  question  as  to  which  type  is  to  be 
approved  will  remain  a  debatable  one.  However,  the  rela- 
tive volumes  in  regard  to  hearth  area,  regenerator  cham- 
bers, etc.,  on  the  basis  of  the  capacity  of  output  per  heat 
will  be  the  same  in  any  style  of  open -hearth  furnace.  The 


OPEN-HEARTH    FURNACE   CONSTRUCTION 


next  in  order  will  be  some  general  rules  as  to  points  of  con- 
struction and  volumes  for  a  2O-ton  unit. 

CONSTRUCTION. — The  metal  work  such  as  buckstays,  tie- 
rods,  hearth  pan,  doors,  etc.,  should  be  of  rigid  construc- 
tion to  withstand  the  heavy  duty  due  to  brick  work  ex- 
pansion when  the  furnace  is  at  full  working  heat.  All 
walls  should  be  bound  at  the  ends.  Rolled  shapes  should 
be  used  whenever  possible.  Skew -backs  of  all  arches 


FIG.    3.— CROSS    SECTION,    STATIONARY   TYPE   OPEN-HEARTH    STEEL 
MELTING  FURNACE. 


should  be  braced  by  the  binding,  particularly  those  of  the 
roof.  In  the  regenerator  chambers  the  ends  of  all  outside 
or  partition  walls  should  be  bound,  as  should  the  ports,  be- 
cause the  brick  expansion  may  cause  leaks  and  permit  igni- 
tion of  the  gas  before  it  reaches  the  working  body  of  the 
furnace.  The  conditions  of  the  subsoil  at  the  selected  site 
should  be  well  studied  before  putting  in  the  foundation. 
Foundations  should  be  of  rigid  and  first-class  masonry  to 
guard  against  irregular  settling.  They  should  be  of  hard 
red  brick  laid  in  cement  or  concrete.  No  part  of  the  fur- 


24  OPEN-HEARTH   FURNACE   CONSTRUCTION 

nace  structure  should  extend  below  the  lowest  point  at 
which  water  may  be  found.  Water  is  an  enemy  to  smooth 
furnace  operation,  if  it  finds  its  way  into  flues  or  chambers. 
All  underground  flues  not  protected  by  clay  should  have 
an  outside  course  of  red  brick. 

The  reversing  valves  should  be  of  such  construction  that 
leakages  and  loss  of  gas  will  not  occur  when  operated. 
There  are  two  distinct  types,  one  known  as  the  "butterfly- 
valves"  and  another  as  the  "turtle-back."  The  latter  is 
water  sealed,  which  is  an  advantage.  The  stack  should 
be  of  such  construction  as  will  induce  a  good  draught,  de- 
pending upon  the  damper  for  regulation. 

Whenever  possible  the  doors,  door  frames  and  furnace 
fronts  should  be  water  cooled,  features  which  add  to  the 
operator's  comfort  in  watching  his  furnace.  The  cost  of 
installation  and  maintenance  may  be  heavy  but  will  result 
in  a  longer  life  for  the  parts  and  a  consequent  lessening  of 
their  repairs  offsetting  the  first  cost.  This  arrangement  is 
only  possible  on  stationary  furnaces.  On  movable  ones  the 
piping  connections,  etc.,  would  be  too  complicated. 

All  flues,  excepting  those  leading  from  the  uptakes  to 
the  furnace  body,  should  be  roomy  to  prevent  choking  and 
cutting  by  the  deposit  and  heat  of  waste  gases.  Roominess 
is  an  essential  in  flues  or  conduits  connecting  the  gas  pro- 
ducers with  the  regulating  and  reversing  valves  and  it  is 
good  practice  to  have  such  conductors  above  ground  the  en- 
tire distance  to  allow  ready  access  for  the  purpose  of 
cleaning  out  unavoidable  accumulations  of  soot  and  tar. 
Gas  flues  or  uptakes  leading  to  the  furnace  body  should  be 
built  with  fake  arches  in  their  back  walls,  so  that  they  can 
be  readily  repaired  when  badly  cut  without  disturbing  the 
rest  of  the  furnace.  They  should  also  slope  towards  the 
hearth  so  that  the  incoming  gas  will  be  directed  downward- 
ly and  impinge  upon  the  stock  or  charge.  The  air  port 
will  also  have  the  same  direction,  and  with  the  gas  and  air 
inlets  and  outlets  working  properly  the  sheet  of  flame  will 


OPEN-HEARTH    FURNACE    CONSTRUCTION 


be  kept  away  from  the  roof  which  will  be  guarded  against 
burning  or  cutting. 

AREAS  AND  VOLUMES. — The  hearth  length  of  an  open- 
hearth  furnace  should  be  as  great  as  possible  in  order  that 
the  greatest  possible  benefit  be  derived  from  the  calorific 
value  of  the  fuel.  An  undue  shortening  would  be  wasteful 
because  the  heat  of  combustion  would  be  spent  in  the  out- 
going gas  and  at  the  sacrifice  of  fuel  consumption  and  ex- 
cessive cutting  of  outlets  leading  to  the  chambers,  meaning 
an  increased  cost  in  furnace  repairs. 

Practical  experience  has  taught  that  a  2O-ton  furnace 
can  be  safely  operated  with  a  hearth  length  of  20-25  feet 
and  a  width  of  9-11  feet.  The  total  area  of  hearth  surface 
will  work  out  to  very  close  to  nine  square  feet  per  ton  of 
capacity.  The  width  is  limited  to  a  maximum  of  15  feet 
because  furnace  operatives  cannot  throw  a  shovelful  of  re- 
fractory material  much  over  that  distance  to  reach  the 
back-wall.  Generally  the  length  will  be  2-2^2  times  the 
width. 

The  depth  of  the  fully  lined  hearth  will  depend  upon  the 
dimensions  of  length  and  width.  A  shallow  bath  will  give 
rapid  working  but  at  the  sacrifice  of  much  burnt  metal  or 
a  yield  which  is  only  a  small  percentage  of  the  metal 
charged.  A  deep  bath  will  retard  the  melting  and  present 
difficulties  in  maintaining  desirable  thermal  conditions. 
The  medium  will  be  learned  by  the  individuality  of  the  fur- 
nace and  conditions  of  practice,  but  to  put  the  problem  in 
figures  the  ranges  for  the  choice  will  be  between  15  inches 
to  20  inches  of  depth. 

An  important  consideration  in  furnace  practice  is  re- 
generator chamber  volumes.  The  fuel  efficiency  will  be 
controlled  largely  by  the  length  of  the  furnace  as  mentioned 
and  also  upon  the  proper  construction  of  the  chambers. 
The  purposes  of  them  will  be  subsequently  considered.  At 
present  attention  will  be  given  to  their  volumes.  In  that 
particular  there  will  be  conditions  to  take  into  account  as 
to  how  much  room  can  be  allowed  by  the  space  in  the  build- 


26  OPEN-HEARTH    FURNACE    CONSTRUCTION 


ing  where  the  furnace  or  furnaces  may  be  located  both 
above  and  below  the  charging  floor  and  the  depth  to  which 
the  foundations  and  flues  can  be  safely  carried.  The  effi- 
ciency of  a  regenerator  chamber  depends  upon  the  number 
of  "checkers"  it  can  carry  and  the  direction  of  incoming 
and  outgoing  gaseous  bodies.  Direction  is  meant  by  the 
flow  of  gases  whether  they  be  nearly  horizontal  or  nearly 
vertical  in  travel. 

In  American  practice  the  longest  dimension  of  the  cham- 
bers is  horizontal,  while  in  European  practice  some  are 
built  with  greater  depth  than  length.  It  would  seem,  in 
view  of  the  natural  tendency  of  heated  gases  to  rise,  that 
the  latter  plan  is  the  better,  but  as  stated  how  they  shall 
be  built  depends  upon  variable  conditions;  however,  with 
a  given  chamber  volume  the  efficiency  varies  with  the 
depth.  There  is  quite  a  range  of  figures  as  to  volumes  of 
regenerators  per  ton  of  capacity  with  different  plants  vary- 
ing from  65  cubic  feet  to  140.  A  good  figure  to  work  by  is 
90  cubic  feet  per  ton,  allowing  1-3  for  gas  and  2-3  for  air 
chambers. 

If  the  fuel  should  be  oil  or  liquid  or  natural  gas  the  vol- 
ume can  be  decreased  materially  because  such  varieties  of 
fuel  are  led  directly  in  the  body  of  the  furnace  instead  of 
passing  through  the  regenerators,  thus  offering  a  possibil- 
ity of  dispensing  with  the  space  occupied  by  regenerators, 
commonly  used  as  ducts  for  producer  gas,  but  it  is  better 
that  a  furnace  be  built  with  an  eye  to  suitability  for  pro- 
ducer fuel  because  the  supply  of  liquid  fuel  or  natural  gas 
is  subject  to  possibilities  of  irregular  deliveries  and  a  fur- 
nace built  only  for  the  latter  fuels  would  cause  some  annoy- 
ances were  they  to  be  short.  By  the  same  token,  producers 
should  always  be  installed  as  a  safeguard  no  matter  what 
fuel  may  be  regularly  used.  Thus  there  would  be  but  lit- 
tle delay  to  put  the  producers  for  gas  into  service  were 
liquid  fuel  or  natural  gas  to  fail. 

The  uses  of  regenerator  chambers  will  next  be  consid- 
ered. The  purpose  is  to  store  in  them  heat  carried  over  by 


OPEN-HEARTH    FURNACE    CONSTRUCTION  2? 


waste  gases  produced  by  the  fuel  combustion  in  the  furnace 
body,  the  heat  being  absorbed  by  a  large  number  of  No. 
i  fire  brick,  piled  in  such  a  manner  that  the  gases  in  their 
travel  from  the  body  of  the  furnace  to  the  stack  will  have 
to  pass  through  innumerable  ducts  or  passages.  Bricks 
piled  in  such  a  manner  are  called  "checkers."  The  plan  is 
to  pile  the  bricks  so  that  they  will  form  rectangular  pass- 
ages of  about  3  to  3^>  inches  in  width.  The  passages  will 
run  horizontally  and  also  vertically.  Sometimes  they  will 
be  in  a  direct  line  in  both  directions,  the  length  and  width 
of  the  chambers  or  the  bricks  may  be  piled  in  such  a  way 
that  the  passages  ,are  zig-zag  or  "staggered."  Generally 
they  are  staggered  in  a  vertical  direction  with  straight 
passages  horizontally. 

DRAFT 

The  question  of  draft  has  to  be  considered  and  with  as 
many  bricks  as  it  may  be  possible  to  checker  and  with  the 
greatest  possible  depth  of  chamber  the  free  working  of 
the  furnace  will  be  augmented  by  straight  passages  in  both 
directions.  Indications  as  to  heat  absorption  by  checkers 
can  be  gauged  by  the  temperature  of  the  waste  gases  enter- 
ing the  stack  with  the  furnace  at  full  working  heat. 

Pyrometrical  observations  by  the  writer  show  the  nor- 
mal working  conditions  of  the  stack  gases  to  be  an  average 
of  500  degrees  Cent,  with  gases  entering  the  outgoing 
down-takes  at  1,400  degrees  Cent,  and  with  air  at  atmos- 
pheric temperatures  entering  chambers  and  passing 
through  them  in  the  up-takes  at  1,000  degrees  Cent,  will 
suggest  the  heat  absorption  and  radiation  of  the  checkers. 

The  temperature  of  combustion  is  not  sufficiently  high  to 
maintain  a  continued  liquation  of  a  bath  of  molten  metal  as 
its  carbon  decreases,  because  the  air  necessary  to  support 
combustion,  even  with  a  forced  draft,  carries  away  or 
absorbs  the  calorific  energy  of  the  flame  playing  upon  the 


28  OPEN-HEARTH    FURNACE    CONSTRUCTION 


bath  of  metal.  In  other  words  cold  air  lessens  the  full 
heating  value  of  combustion  that  should  otherwise  be  spent 
in  work.  If,  then,  the  temperature  of  the  necessary  air  for 
complete  combustion  be  raised,  to  that  extent  will  the  flame 
efficiency  be  increased.  On  that  rests  the  principle  of  re- 
generation. 

Let  the  course  of  the  air  be  followed  in  the  chambers  of 
an  open-hearth  furnace  passing  from  left  to  right.  The 
reversing  valves  are  in  position  to  direct  the  inflow  of 
gas  and  air  in  their  respective  chambers  on  the  left  side  of 
the  furnace.  Passing  through  the  checkers  and  innumer- 
able ducts,  they  enter  the  up-takes.  The  gas  upon  reaching 
the  furnace  body  immediately  ignites  and  draws  upon  the 
accompanying  air  for  complete  combustion,  the  respective 
volumes  of  each  being  under  control  by  the  operator.  The 
flame  energy  being  dissipated  in  work,  the  waste  gases  are 
now  drawn  by  the  draft  and  pushed  along  by  a  rear  expan- 
sion towards  the  stack  but,  before  reaching  it,  nearly  all 
their  heat  units  are  absorbed  by  the  checkers  in  the  right- 
hand  set  of  chambers.  After  an  interval  of  15  to  20  minutes 
the  reversing  valves  are  thrown  and  the  gases  are  reversed 
in  direction.  The  air  and  gas  now  passing  into  the  already 
heated  right-hand  chambers  carry  back  by  radiation  to  the 
furnace  body  some  of  the  waste  heat  previously  deposited 
there  to  add  to  the  heat  units  produced  by  combustion. 
The  efficiency  of  the  flame  will  be  greater  from  the  right- 
hand  chambers  work,  assuming  both  sets  to  be  of  an  equal 
temperature  at  the  beginning  of  the  operation,  and  after 
the  second  reversal  the  left-hand  chamber  will  bring  a  still 
greater  increment  of  heat  value  than  its  neighbor.  That  is 
to  say,  the  heat  units  radiated  to  the  incoming  air  and  in- 
creasing the  flame  value  necessarily  permits  more  heat  for 
the  outgoing  checkers  to  absorb.  Thus  it  will  be  seen  that 
with  the  increase  in  the  number  of  reversals  there  will  also 
be  a  gain  in  heat  for  work. 

It  would  be  possible  to  melt  the  best  refractories  by 
reaching  high  ranges  of  temperature  by  the  principle  of  re- 


OPEN-HEARTH    FURNACE   CONSTRUCTION  29 

generation  but  by  careful  watching  on  the  part  of  the  ope- 
rator, flame  and  air  volumes  are  properly  regulated  to  pre- 
vent burning  of  the  furnace.  At  the  same  time,  enough 
heat  must  be  maintained  during  the  progress  of  a  melt  to 
preserve  the  fluidity  and  proper  temperature  of  a  bath  of 
steel  at  proper  intervals.  Without  the  system  of  regen- 
eration it  would  not  be  possible  to  successfully  handle  200 
tons  or  less  of  liquid  steel  at  a  time  in  a  single  operation  of 
an  open-hearth  furnace. 

The  speed  at  which  the  gases  travel  through  the  furnace 
when  working  is  due  to  both  draft  and  expansion.  As 
soon  as  the  cold  incoming  air  comes  in  contact  with  the 
heated  checkers  it  immediately  expands  and  produces  a 
slight  pressure  which  forces  the  body  of  air  before  it  up- 
wardly, and  entering  the  furnace  body  it  not  only  assists 
the  combustion  of  the  fuel^  but  washes  and  protects,  so  to 
speak,  the  roof  of  the  furnace  with  a  film  of  air  and  at  the 
same  time  depresses  the  flame  upon  the  bath  of  metal. 
With  free  passages  in  the  down-takes  and  checkers,  the 
stack  will  readily  take  care  of  the  waste  gases.  Obstruc- 
tions in  either  would  make  a  slow  working  furnace  and 
disagreeable  waste  of  flame  out  of  the  furnace  doors. 

Another  important  feature  about  regenerative  chambers 
is  that  they  should  never  be  under  the  furnace  body  or  have 
their  up-takes  directly  below  the  ports.  In  the  first  in- 
stance there  would  be  danger  of  irregular  settling  causing 
cracks  in  the  partition  walls  between  the  air  and  gas  cham- 
bers, which  would  allow  gas  leakages  and  ignition  of  same 
before  entering  the  furnace.  In  the  second  place  there  is 
always  more  or  less  dust  and  slag  carried  along  by  the 
draft  which  would  be  deposited  in  the  checkers  with 
chambers  located  as  just  mentioned,  thus  choking  them  and, 
of  course,  crippling  their  life.  Good  practice  requires  that 
the  chambers  be  placed  at  the  furnace  ends  and  extend  at 
right  angles  to  them  under  the  charging  floor.  There 
should  also  be  spacious  receptacles  at  the  lowest  point  of 
each  down-take  to  retain  accumulations  of  dust  and  slag 


30  OPEN-HEARTH    FURNACE   CONSTRUCTION 


before  they  could  reach  the  chambers.  Such  are  known 
as  slag  pockets  and  with  proper  construction  they  can  read- 
ily be  cleaned  out  without  disturbing  the  checkers. 


ACID  FURNACE   BRICK   WORK 

The  furnace  body  wherever  subjected  to  uniform,  high 
temperature  is  lined  by  first  grade  silica  bricks.  Piers  and 
outside  walls  of  the  structure  below  the  charging  floor  can 
be  red  brick;  linings  of  flues  and  chambers  including 
checkers  are  No.  I  fire  brick.  Silica  brick  will  not  answer 
for  checkers  because  they  will  crumble  under  the  varying 
ranges  of  heat. 

The  hearth  pan  is  lined  with  fire  brick  to  the  depth  of 
nine  inches  or  more,  but  above  metal  line  of  a  fully  lined 
hearth,  the  sides,  walls  and  roof  are  silica.  With  the  brick 
work  complete  the  furnace  is  first  dried  moderately  and 
carefully  with  a  wood  or  soft  coal  fire  kept  going  for  a  few 
days. 

The  gas  or  oil  can  then  be  turned  on  slightly  at  first  and 
then  gradually  raised  to  nearly  full  working  temperature. 
Layers  of  silica  sand  of  the  quality  described  in  chapter  I 
are  then  spread  over  the  bottom.  They  are  put  in  in  suc- 
cession and  between  each  interval  the  flame  is  allowed  to 
set  or  sinter  the  sand  until  hard.  This  operation  is  repeated 
until  the  hearth  lining  will  have  reached  a  depth  of  18  to 
20  inches  including  the  fire  bricks.  A  hearth  so  lined  with 
a  suitable  refractory  ought  to  last  almost  indefinitely  under 
favorable  conditions. 

There  will  be  occasional  patching  of  the  slag  line  and 
bottom  with  sand,  at  the  end  of  each  heat,  the  extent  of 
which  will  be  controlled  by  the  conditions  and  character 
of  stock  used  in  melting.  A  hearth  properly  lined  must  be 
set  hard  enough  to  resist  attrition  by  the  charging  of  melt- 
ing stock.  Under  skillful  handling  an  acid  furnace  ought 


OPEN-HEARTH   FURNACE    CONSTRUCTION  3! 


to  turn  out  normally  950  heats  or  more  in  a  campaign  at 
the  rate  of  at  least  3  heats  per  working  day. 


BASIC  FURNACE  BRICK  WORK 

The  designation  basic  is  rather  a  misnomer.  The  nature 
of  the  basic  process  requires  a  lining  of  such  materials  that 
will  resist  the  fluxing  action  of  limey  slags  and  vapors  nec- 
essary to  purify  and  refine  phosphoric  melting  stock.  Un- 
fortunately no  materials  are  commercially  available  to  com- 
pletely line  a  furnace  body,  so  recourse  can  only  be  had  to 
a  hearth  lined  with  basic  materials,  with  roofs,  sides  and 
walls  of  furnace  body  above  the  slag  line  consisting  of 
silica  or  acid  bricks,  the  reasons  being  that  bricks  of  basic 
or  neutral  material,  such  as  magnesite  or  chrome,  while  be- 
ing refractory,  do  not  give  as  good  results  as  silica  bricks, 
owing  to  a  liability  to  crumble  if  placed  in  the  walls  or  roof. 
Therefore  a  basic  furnace  is  part  acid  and  part  basic  lining. 

With  the  exception  of  the  furnace  body  in  regard  to  brick 
work,  the  construction  is  the  same  as  an  acid  furnace.  The 
hearth  pan  is  first  lined  with  fire  brick  followed  with  mag- 
nesite bricks.  Usually  the  bottom  is  lined  with  ground 
magnesite.  It  may  be  mixed  with  about  5  per  cent  of 
anhydrous  tar  and  rammed  in  to  form  the  hearth  and  then 
slowly  and  carefully  brought  to  full  temperature;  or  the 
magnesite  may  be  put  in  loosely  in  layers  and  gradually  sin- 
tered. A  small  percentage  of  ground  basic  slag  is  some- 
times mixed  with  it  to  insure  a  partial  fusing  or  sinter. 

A  magnesite  hearth  while  costly  gives  the  best  results  in 
service  and  will  sinter  hard  enough  to  withstand  rough 
usage  by  charging  of  the  stock.  Where  the  magnesite 
bricks  meet  the  silica  bricks  of  the  walls,  a  parting  of 
chrome  ore  is  placed  as  a  neutral  separation  of  the  two  to 
prevent  a  fluxing  liable  to  ensue  between  them  at  full  work- 
ing temperature. 

There  will  always  be  some  scorification  of  the  hearth  at 


32  OPEN-HEARTH    FURNACE   CONSTRUCTION 


the  slag  line  and  an  occasional  formation  of  holes  in  the 
bottom,  due  to  the  action  of  silicious  matter  carried  in  with 
the  stock.  The  repairs  to  the  hearth  are  made  with  raw 
dolomite  on  the  slag  line,  and  with  ground  magnesite  on 
the  bottom.  Dolomite  being  so  much  cheaper  it  is  fully  as 
effective  as  magnesite  at  the  slag  line.  In  the  raw  state  it 
is  not  recommended  for  bottom  repairs,  because  at  a  high 
temperature  it  is  calcined,  contracting  greatly  in  bulk  and 
for  that  reason  holes  in  the  bottom  cannot  be  satisfactorily 
filled  with  it.  Under  the  heat  of  fused  stock  it  would 
loosen,  float  upwards,  and  leave  the  condition  as  bad  as  be- 
fore the  patch. 

Undue  hearth  scorification  can  be  controlled  by  proper 
care  in  the  character  of  stock.  Hence  the  consumption  of 
refractories  for  hearth  patching  can  be  kept  at  the  mini- 
mum figure.  With  proper  case  a  basic  hearth  of  magnesite 
should  last  indefinitely,  and  the  life  of  the  brick  work  of 
the  roof  and  walls  ought  to  yield  400  or  more  heats  at  3 
heats  per  day. 


CHAPTER  III 


FUELS   AND  ACCESSORIES — DISCUSSION   OF   THE   USES   OF 
COAL  AND  OIL 

As  the  choice  of  fuel  may  rest  between  producer  gas  or 
oil,  a  description  of  the  operation  of  either  will  be  briefly 
considered.  Referring  to  the  illustration  of  a  gas  producer, 
Fig.  4,  a  general  idea  will  be  formed  of  its  construction. 
The  one  shown  is  of  the  simpler  kind  and  entirely  hand  fed 
and  poked.  In  some  of  the  large  rolling  mills  coal  is  fed 
in  continuously  by  a  mechanical  device,  and  the  bed  of  the 
fuel  is  poked  by  a  mechanical  contrivance.  The  principle 
of  operation  is  the  same  in  either  case  so  far  as  making 
gas  goes. 

For  a  continuous  supply  of  gas,  air  and  steam  are  forced 
through  an  incandescent  bed  of  bituminous  coal  on  top  of 
which  is  fed  at  regular  intervals  fresh  coal.  Frequently  the 
mass  is  poked  with  long  bars  to  break  up  the  decomposing 
coal  and  to  prevent  holes  or  passages  being  formed  which 
might  allow  air  to  pass  through  them  and  dilute  the  gas. 
In  the  vicinity  of  the  grate,  which  is  water  sealed,  the  fuel 
is  completely  burned,  while  near  the  top  the  fuel  gives  off 
its  volatile  matter,  forming  copious  volumes  of  smoke  with 
some  tarry  matter.  As  the  fuel  descends  towards  the  grate 
it  is  gradually  burned  to  ash. 

For  proper  working  conditions  the  bed  of  coal  should 
be  kept  at  a  constant  height,  and  vigorous  poking  should  be 
frequently  and  persistently  followed. 


34 


FUELS  AND  ACCESSORIES 


The  object  of  water-sealing  the  grate  is  to  permit  the 
amount  of  air  necessary  to  gasify  the  coal,  to  be  under  con- 
trol at  all  times. 

The  use  of  steam  lessens  the  temperature  of  combustion 


lop  Vleiv  of  Water  Flan, 


Section  E- 


FIG.  4. — GAS  PRODUCER. 


at  the  grate  and  so  lengthens  the  life  of  the  grate  bars.  At 
the  same  time  the  steam  chemically  combines  with  the  fuel 
to  form  water  gas  as  will  be  shown.  It  also  prevents  the 


FUELS  AND  ACCESSORIES  35 

formation  of  clinkers,  making  it  easier  to  keep  the  fires 
clean. 

To  make  good  gas  the  fuel  must  be  hot,  and  close  attention 
must  be  given  to  the  admixture  of  air  and  steam  forced  into 
the  producer.  Too  much  steam  tends  to  cool  the  fires  and 
pass  into  the  flues,  undecomposed,  causing  an  extravagant 
loss  of  fuel  efficiency.  A  deep,  hot  bed  of  coal  will  yield 
the  richest  gas. 

It  will  not  be  amiss  to  consider  some  of  the  chemical 
changes  that  take  place  in  a  producer.  Roughly  the  bed 
of  fuel  in  it  can  be  divided  into  two  zones.  The  lower 
one,  nearest  the  grate,  can  be  called  the  CO2  zone  and  the 
upper  one  the  CO  zone.  The  air  coming  into  union  with  the 
fuel  near  the  grate  forms 

C  +  2  O  =  CO. 

CO2  is  of  course,  non-combustible,  but  as  it  passes  up- 
wards it  combines  with  the  glowing  carbon  of  the  CO  zone 
and  absorbing  some  becomes 

CO2  +  C  =  2CO. 

the  latter  constituent  forming  the  larger  volume  and  chief 
calorific  agent  of  producer  gas.  By  the  action  of  steam  we 
have 

C  +  HsO  =  CO  +  2H  (water  gas). 

The  calorific  value  of  this  last  product  is  greater  in  equal 
volume  than  the  CO  formed  in  second  equation  but  at  the 
expense  of  the  heat  in  the  bed  of  fuel.  The  following  is 
an  analysis  of  producer  gas  by  volume : 

C  O   27.00  per  cent 

C  O2   5.00  per  cent 

H   10.00  per  cent 

C  H4  -f  C2  H4  1.50  per  cent 

O  +  N  by  difference  56.50  per  cent 

100.00  per  cent 
The  amount  of  oxygen  in  the  gas  will  be  about  I  per  cent, 


FUELS  AND  ACCESSORIES 


and  represents  the  air  that  passes  through  the  producer 
uncombined.  The  index  to  the  proper  working  of  the  pro- 
ducer is  the  amount  of  COs  present.  Under  the  most  ad- 
vantageous conditions  it  will  rarely  fall  below  2.5  per  cent 
and  with  bad  conditions  it  will  exceed  the  average  of  5 
per  cent.  The  causes  of  an  excess  are  due  to  insufficient 
poking,  a  shallow  fire  and  faulty  brick  work  allowing  air 
leakage  to  ignite  the  gas  before  it  can  be  delivered  to  the 
furnace. 


9  Threads  to  \'J        ,,  Thrcafl!i  to  r 


Rubber  Hose 
Connects  Here 


FIG.   5. — OIL   BURNER   FOR   OPEN-HEARTH    FURNACE 


At  the  best,  producer  gas  is  unsatisfactory,  and  the  steel 
melter  is  always  at  the  mercy  of  the  vigilance  or  lack  of 
it  of  the  gas  man. 

One  ton  of  bituminous  coal  yields  160,000  to  170,000 
cubic  feet  of  gas  with  a  calorific  value,  at  the  producer,  of 
about  137  B.  T.  U.  per  cubic  foot.  The  gas  in  traveling 
to  the  furnace  loses  heat  units  at  a  variable  rate.  The 
actual  amount  of  gas  delivered  to  the  furnace  is  hard  to 
determine,  owing  to  leakage  and  the  consumption  in  drying 
ladles. 


FUELS  AND  ACCESSORIES 


37 


Liquid  fuels,  such  as  crude  petroleum  or  residuum,  pos- 
sess a  high  calorific  value,  usually  expressed  at  14,000  to 
17,000  B.  T.  U.  per  pound  of  oil.  Because  the  oil  being 
delivered  directly  to  the  furnace  (see  oil  burning  device 
and  furnace  construction  for  same,  Figs.  5  and  6),  and 
igniting,  when  atomized  by  steam  or  compressed  air, 
yields  its  entire  thermal  efficiency  to  work  with  no  interme- 
diate losses  as  is  the  case  with  gas,  the  value  of  oil  over 
the  latter  is  marked. 


FIG.   6. — FURNACE   ARRANGED   FOR   BURNING  OIL 

It  is  difficult  to  make  an  actual  comparison  between  oil 
and  coal  for  steel  melting  on  the  basis  of  the  cost  of  a  ton 
of  metal  produced.  The  figures  may  be  in  favor  of  coal 
in  certain  localities,  and  in  favor  of  oil  in  others.  Yet  the 
advantages  of  oil  over  coal  in  working  results  are  so  pro- 


38  FUELS  AND  ACCESSORIES 


nounced  that  discrepancies  in  cost  against  oil  are  offset  by 
its  usefulness. 

Ignoring  the  relative  costs,  the  principal  points  in  favor 
of  oil  against  gas  will  be  considered. 

First,  the  higher  thermal  value:  A  cubic  foot  of  gas 
will  yield  137  B.  T.  U.  Taking  16,000  B.  T.  U.  as  an 
average  of  one  pound  of  oil  and  allowing  a  cubic  foot  of 
oil  at  57.11  pounds  then  57.11  X  16,000  =  913,760  B. 
T.  U.  a  substantial  gain  in  favor  of  oil  against  an  equal 
volume  of  gas. 

Second,  the  simplicity  of  installation.  One  furnace  will 
require  a  storage  tank  with  a  capacity  of  about  17,000 
gallons.  From  this  the  oil  is  pumped  to  the  burner  which 
essentially  is  the  producer  in  the  sense  that  the  arrange- 
ment .of  the  burner  permits  a  necessary  atomization  of  the 
oil  by  steam  or  compressed  air  before  ignition.  It  is  su- 
perfluous to  make  a  further  comparison  on  this  point,  in 
view  of  the  crudity  of  the  gas  producer. 

Third.  The  use  of  oil  lessens  furnace  repair  costs  and 
allows  longer  campaigns  before  shutting  down  for  general 
repairs.  This  point  alone,  is  perhaps  the  strongest  one  in 
favor  of  oil.  Conditions  of  brick  work  in  regenerator 
chambers  do  not  require  the  same  attention  with  liquid 
fuel  as  they  would  with  gas.  That  is  to  say,  should  there 
be  leakages  in  the  partition  wall  between  air  and  gas 
chambers,  they  can  be  ignored,  using  oil;  but  with  gas 
they  would  necessitate  a  shut-down  of  the  furnace  to  re- 
pair them.  The  same  applies  to  ports  and  down-takes. 

Fourth.  The  character  of  the  oil  not  being  subject  to 
the  same  latitudes  of  irregularity  as  the  composition  of  the 
gas,  there  results  a  decided  gain  in  the  certainty  of  the 
furnace's  work.  The  temperature  of  the  bath  is  under 
control,  and  regularity  of  output  can  be  expected — a  feat- 
ure not  so  dependable  with  gas. 

Fifth.  The  labor  cost  is  greatly  lowered.  One  man  per 
working  day  attends  the  pumps.  In  the  gas  house  there 
will  be  a  foreman  and  several  laborers  to  feed  and  poke  the 


FUELS  AND  ACCESSORIES  39 

fires,  and  to  wheel  away  the  ashes.  The  labor  in  unloading 
and  stocking  coal  is  also  eliminated.  With  these  features 
can  be  mentioned  the  removal  of  the  attendant  dirt  and 
smoke  with  gas  producers;  the  loss  of  time  in  cleaning 
gas  mains  and  other  conditions  that  would  occupy  too  much 
space  to  mention. 

Oil  fuel  will  also  be  useful  for  drying  ladles,  firing  an- 
nealers,  core  ovens,  etc. 


CHAPTER  IV 

MANIPULATION  OF  HEATS  IN  ACID  PRACTICE — COMPOSI- 
TION OF  CHARGES — DETAILS  OF  RECARBONIZING 

Given  an  acid  lined  hearth  and  stock  for  melting  pur- 
poses, the  next  step  will  be  to  consider  some  of  the  changes 
that  take  place  in  the  conversion  of  the  materials  charged 
into  steel.  As  has  been  mentioned  the  only  elements,  that 
are  confined  within  stated  limits,  are  the  sulphur  and 
phosphorus.  Considerable  latitude  remains  in  making  up 
the  charge  in  regard  to  the  available  silicon,  carbon  and 
manganese  carried  in  by  the  stock.  Assuming  the  stock 
to  be  made  up  of  pig  iron,  billets,  blooms,  plate-clippings, 
axle-butts,  defective  steel-castings,  shop  scrap  or  wasters 
in  varying  proportions,  a  charge  of  24,000  pounds  will  be 
studied  because  the  diagram  herewith  shown  (Fig.  7)  was 
plotted  on  a  heat  of  that  size.  The  proportions  and 
changes  would  be  relatively  the  same  in  a  2O-ton  heat. 

The  charge  will  be  as  follows:— 


Acid    pig    iron     —    3,600 

Mixed   scrap         =  20,400 

Lbs.       24,000 


15  per  cent 

85  per  cent 

100  per  cent 


AVERAGE  COMPOSITION 

C  0.90  per  cent 

Mn  0.47  per  cent 

Si  0.40  per  cent 

S  0.024  per  cent 

P  0.028  per  cent 


MANIPULATION   OF   HEATS   IN  ACID   PRACTICE  4! 

The  order  of  charging  will  be  as  follows : — 
First. — Two-thirds  of  the  pig  iron. 
Second. — Lightest  sections  of  scrap. 
Third. — Heaviest  sections  of  scrap. 
Fourth. — One-third  or  remainder  of  pig  iron. 

The  object  in  charging  the  pig  iron  in  two  portions  with 
the  larger  amount  on  the  bottom  is  to  protect  it  from  scori- 
fication  caused  by  the  oxide  of  iron  always  formed  in  the 
melting  of  the  scrap  which  oxidizes  at  a  faster  rate  than  the 
pig  iron.  The  portion  of  pig  iron  on  top  is  the  first  to  melt 
and  in  dripping  over  the  scrap  lowers  the  melting  point  of 
the  latter  and  in  a  measure  protects  it  from  undue  burn- 
ing or  oxidation  until  the  whole  mass  sinks  below  the  slag 
formed  during  the  exposure  of  the  stock  to  the  flame  action. 

The  length  of  time  occupied  in  charging  varies  as  to  the 
size  of  the  pieces  of  scrap  charged  and  the  room  it  offers  to 
follow  with  the  rest  of  the  stock. 

Occasionally  there  may  be  some  little  time  elapse  before 
the  bulky  stock  may  have  partly  melted  and  subsided  before 
the  charge  can  be  completed.  Usually  the  length  of  time 
consumed  in  charging  is  about  one  to  one  and  one-half 
hours. 

The  charging  of  stock  being  completed  the  history  of  the 
heat  is  divided  into  two  stages :  First,  the  melting ;  second, 
the  complete  fusion  and  conversion  of  the  materials.  Dur- 
ing the  first  period  little  or  no  change  takes  place  in  the 
composition,  the  main  action  being  the  transmission  of  the 
solid  stock  to  the  liquid  form  and  with  it  the  formation  of 
the  slag  which  is  to  play  an  important  part  in  the  subsequent 
conversion  of  the  stock  to  steel. 

The  length  of  time  required  to  liquify  the  stock  is  normal- 
ly from  2  to  2^2  hours,  and  during  that  time  the  tempera- 
ture of  the  furnace  is  gradually  increasing  owing  to  the 
method  of  regeneration  already  explained. 

It  is  certain  that  some  changes  occur  as  soon  as  the  stock 
begins  to  melt  and  the  slag  begins  to  form.  Perhaps  the 
most  pronounced  change  takes  place  by  flame  action  on  the 


MANIPULATION  OF   HEATS   IN   ACID  PRACTICE 


Diagram  Showing  Variations  in  Composition 
of  a  Formal  A.ci<l 
Open  Hearth  Heat 


FIG.   7 —  SHOWS  VARIATION   IN    COMPOSITION   OF   A   NORMAL   ACID 
OPEN-HEARTH  HEAT 


MANIPULATION   OF  HEATS  IN  ACID  PRACTICE  43 


exposed  stock,  it  being  strongly  oxidizing ;  but  not  until  the 
charge  becomes  entirely  fused  or  liquid  does  the  active  part 
of  conversion  begin. 

With  complete  liquation  of  the  charge  the  flame  simply 
becomes  a  vehicle  of  heat  and,  under  the  practiced  eye  of 
the  melter,  the  thermal  conditions  are  so  maintained  that 
the  temperature  of  the  bath  is  gradually  increased  as  the 
conversion  progresses.  It  is  necessary  that  the  tempera- 
ture of  bath  be  gradually  increased  because  of  the  influ- 
ence of  carbon.  In  general  terms  the  fusing  point  of  iron 
or  steel  depends  upon  the  amount  of  that  element,  the  high- 
er percentage  fusing  at  a  lower  point  thermometrically 
than  the  lower  amounts. 

Glancing  at  the  diagram  the  carbon  will  be  seen  as  gradu- 
ally increasing  as  the  conversion  progresses.  Without  a 
corresponding  increase  in  temperature,  the  bath  of  metal 
would  become  pasty ;  and  with  the  bath  in  that  condition 
there  would  be  losses. 

In  order  to  induce  liquation  at  the  first  stage  of  conver- 
sion it  is  necessary  to  introduce  carbon  in  addition  to  that 
being  furnished  by  the  pig  iron  of  the  charge.  Fluidity 
and  proper  thermal  conditions  succeeding  are  then  easily 
attained. 

Assuming  the  stock  to  be  melted  and  having  passed  from 
direct  flame  action  below  a  covering  of  slag  the  functions 
of  that  will  next  be  considered.  The  existence  of  the  slag 
is  derived  from  sand  carried  in  mechanically  by  the  stock, 
the  oxidation  of  the  silicon  contained  in  the  pig-iron  and 
scrap  to  silica,  the  oxidation  of  the  manganese  brought  in 
by  them  to  manganous  oxide,  some  scprification  of  the 
hearth  and  the  oxidation  of  iron  to  ferrous  oxide. 

Normally  the  slag  is  automatically  formed,  in  regard  to 
composition,  throughout  the  progress  of  the  heat. 

Should  there  be  an  excess  of  FeO  due  to  low  silicon 
pig-iron,  there  would  be  an  excessive  cutting  of  the  hearth 
and  it  might  be  necessary  to  add  sand  to  furnish  the  needed 
SiO  to  form  the  adjustment  of  proper  slag  composition. 


/| /j  MANIPULATION  OF  HEATS  IN  ACID  PRACTICE 

Approximately  a  normal  slag  in  an  acid  heat  consists  of 
nearly  equal  parts  SiOa  acid  and  FeO  +  MnO  (bases)  and 
this  composition  will  exist  throughout  the  heat  with  a  grad- 
ual increase  in  volume  resulting  from  the  continued  oxi- 
dation of  silicon  and  manganese  and  by  the  addition  of 
iron-ore. 

The  oxidation  of  the  carbon  causes  a  lively  bubbling  in 
the  bath  by  the  liberation  of  carbon  monoxide  (CO)  as  a 
result  of  the  exchange  between  the  FeO  of  the  slag  and  the 
oxygen  furnished  by  iron-ore  additions,  which  may  be  ex- 
pressed as  follows: 

C  +  O^CO  or  C  +  FeO  =  Fe  +  CO. 

The  metallic  iron  reduced  from  the  FeO  of  the  slag  and 
that  brought  in  by  the  iron  ore  (FezOs)  is  immediately  ab- 
sorbed by  the  bath.  Were  there  no  additions  of  ore  the 
slag  would  become  thick  and  pasty  owing  to  the  decrease 
of  the  base  FeO. 

Test  samples  should  be  taken  regularly  after  melting,  the 
fractions  of  which  indicate  the  amount  of  carbon  in  them, 
giving  guidance  to  the  melter  as  to  the  necessary  additions 
of  ore. 

In  acid  practice,  only  the  carbon  is  considered  in  pre- 
liminary tests,  but  for  detailed  information  they  may  be  ex- 
amined for  the  usual  elements.  When  in  the  judgment  of 
the  melter  the  bath  needs  no  more  iron  ore  and  the  decreas- 
ing carbon  has  reached  a  predetermined  point  (which  can 
be  accurately  estimated  by  the  practiced  eye)  preparations 
are  then  made  to  finish  the  heat. 

The  thermal  conditions  being  satisfactory  and  the  slag 
normal,  deoxidizers  and  recarburizers  in  the  shape  of  ferro- 
silicon  and  ferro-manganese  are  then  added  and  the  heat  of 
finished  steel  is  ready  to  tap  or  draw  off  into  a  hot  ladle. 

DETAILS   OF   RE-CARBONIZING 

Assuming  that  the  chemical  composition  of  the  metal 
going  into  castings  shall  be  as  follows : 


MANIPULATION  OF  HEATS  IN  ACID   PRACTICE  45 


C    0.25  per  cent 

Si    0.300  per  cent 

S    0.040  per  cent  or  less 

P    0.040  per  cent  or  less 

Mn    0.75  per  cent  or  less 

which  may  be  considered  as  representative  of  regular  prac- 
tice on  medium  hard  cast-steel.  Taking  as  a  basis  24,000 
pounds  of  metal  charged  and  the  weights  of  ferro-silicon 
and  ferro-manganese  792  and  305  pounds  respectively,  from 
them  there  will  be  furnished  silicon,  manganese  and  carbon 
plus  those  several  elements  contained  in  the  bath  at  the  time 
of  final  additions.  According  to  these  analyses  the  available 
elements  will  be  first,  silicon  from  the  FeSi  with  10  per  cent 
silicon, 

792  X  o.io  =  79.2  pounds  Si; 

second,  manganese  from  the  FeMn  with  80  per  cent  manga- 
nese, 

305    X   0.80  =  224  pounds   Mn; 

third,  carbon  from  both  the  FeSi  and  FeMn. 

792  .X   0.015  =  11.88 
305   X   0.055  =  16.77 

28.65  Ibs.  C 

Taking  into  account  the  residual  silicon,  manganese  and 
carbon  of  the  bath,  and  adding  to  them  those  furnished  by 
the  FeSi  and  FeMn  there  will  be, 

Si  =  o.oooi  X  24,000  +  79.2  =  81.6  total  available 
Mn^  0.0003  X  24,000  +  244.0  =  251.2  total  available 
C  =  0.0012  X  24,000  +  28.7  =  57.5  total  available 

With  the  number  of  pounds  of  the  several  elements  di- 
vided by  the  weight  of  the  charge  there  will  be  found  the 
approximate  analysis  of  the  finished  product, 


46  MANIPULATION  OF  HEATS  IN  ACID  PRACTICE 


100   X      8l.6 

ioo  X  251.2 
ioo  X     57.5 


24,000  =  0.34  per  cent  Si 
24,000  =•  1.05  per  cent  Mn 
24,000  =  0.24  per  cent  C 


or  calculating  another  way  the  approximate  composition  can 
be  determined  in  finished  product  using  the  same  quantities 
of  values  in  terms  of  available  silicon,  manganese  and  car- 
bon:— 


ioo  X  79.2        Residual 

+  o.oi  =  0.34  per  cent  Si 

24,000 

ioo  X  244 

+  0.03  =  1.05  per  cent  Mn 

24,000 

ioo  X  28.65 

+  0.12  =  0.24  per  cent  C 

24,000 

In  making  the  foregoing  computations  the  amounts  of 
sulphur  and  phosphorus  have  been  ignored.  With  a  slag 
highly  charged  with  silica  no  absorption  of  these  takes  place, 
and  the  amount  of  either  carried  in  by  the  melting  stock 
nearly  equals  the  finished  product  in  regard  to  their  con- 
tent. Usually  there  are  slight  gains.  The  sulphur  increases 
because  of  flame  contamination  and  a  loss  of  metallic  iron 
by  oxidation.  Phosphorus  also  increases  slightly  through 
the  latter  cause.  Both  may  be  slightly  augmented  by  move- 
ments from  the  deoxidizers. 

The  chemical  composition  as  shown  in  the  foregoing  fig- 
ures will  differ  from  that  shown  by  the  ultimate  analysis 
of  a  sample  taken  when  the  steel  is  going  into  the  molds. 
Comparing  the  approximate  and  ultimate  figures  we  find: 

Approximate  Ultimate 

Analysis.  Analysis. 

C    0.24  per  cent  0.22  per  cent 

Mn    1.05  per  cent  0.71  per  cent 

Si    0.34  per  cent  0.31  per  cent 


MANIPULATION   OF   HEATS   IN   ACID   PRACTICE 


The  main  difference  is  between  the  manganese  added  and 
that  found,  the  cause  of  which  will  be  understood  in  the  ex- 
planation of  the  purpose  in  using  the  deoxidizing  agents 
FeSi  and  FeMn.  During  the  second  stage  of  the  conver- 
sion, the  bath  of  molten  metal  carries  variable  quantities  of 
dissolved  ferrous  oxide  (FeO)  and  with  that  substance 
there  is  a  vigorous  chemical  action  between  the  carbon  and 
the  oxygen  of  the  FeO  producing  throughout  the  bath  co- 
pious bubbles  of  the  gas  CO.  So  long  as  the  bath  remains 
liquid  this  chemical  action  will  go  on,  charging  it  with  that 
gaseous  body.  Were  the  metal  in  that  condition  to  be 
poured  into  castings  they  would  be  found  to  be  unsound  or 
honey-combed  with  blow  holes. 

Since  solidity  of  product  is  one  of  the  objects  sought  in 
the  physical  properties,  recourse  must  be  had  to  some  agent 
or  agents  that  will  remove  the  cause  of  the  gas-forming 
action  in  the  bath  of  metal  before  it  can  be  drawn  off.  The 
agents  must  possess  greater  affinity  for  the  oxygen  of  the 
dissolved  FeO  than  the  carbon  in  intimate  association  with 
it.  Practical  experience  has  shown  that  manganese  and  sili- 
con accomplish  the  purpose  and  these  elements  are  com- 
mercially available  in  the  alloys,  FeMn  and  FeSi.  Hence 
their  designation  as  deoxidizers.  The  functions  may  be  ex- 
pressed as  follows  : 

(1)  FeO  +  Mn  =  Fe  +  MnO 

(2)  F2FeO  +  Si  —  Fe2  +  SiO2 

In  the  interchange  between  the  C  and  the  FeO  we  have 
a  gas  impregnating  the  bath.  In  the  interchange,  as  shown 
in  the  above  equations,  we  have  a  solid  or  an  easily  fusible 
slag  formed  by  the  SiO2  and  the  MnO,  which  being  lighter 
than  the  molten  metal  quickly  floats  to  the  surface  of  the 
bath.  Thus  with  normal  conditions  the  metal  will  cease  bub- 
bling and  pour  quiet  or  "dead"  and  tend  to  make  solid  cast- 
ings. 

The  amounts  of  silicon  and  manganese  in  the  finished 
metal  will  in  the  main  depend  upon  the  condition  of  the  bath 


48  MANIPULATION   OF   HEATS   IN   ACID  PRACTICE 


at  the  time  the  deoxidizers  are  added,  and  the  difference  in 
analyses  between  the  approximate  and  ultimate  figures  may 
be  taken  to  represent  the  amount  consumed  in  "washing" 
the  bath  of  metal. 

The  usual  practice  in  adding  the  deoxidizers  is  as  follows : 
The  carbon  having  dropped  to,  say,  o.io  to  0.12  per  cent, 
the  dose  of  FeSi,  broken  into  short  pigs,  is  placed  on  the 
breast  of  the  furnace  in  order  to  heat  it  up  before  pushing 
it  into  the  bath.  After  a  lapse  of  about  eight  minutes  the 
whole  is  pushed  into  the  bath,  allowing  a  little  time  to  pass 
during  which  the  FeSi  is  melting  and  dissolving.  To  in- 
sure a  complete  distribution  the  bath  is  agitated  with  bars 
of  iron.  Ten  minutes  after  the  FeSi  is  added  the  metal  is 
ready  to  tap,  but  before  doing  so,  the  dose  of  FeMn  is 
thrown  in  and  then  the  tapping  may  take  place.  It  is  some- 
times the  practice  to  put  part  of  the  FeMn  into  the  fur- 
nace and  part  into  the  ladle,  the  latter  being  done  while  the 
steel  is  flowing  into  it. 

In  an  acid  heat  the  losses  of  silicon  in  the  act  of  deoxidiz- 
ing are  not  great,  but  of  the  manganese  used  for  the  same 
purpose,  considerable  is  consumed,  being  greater  when  en- 
tirely added  to  the  furnace  than  when  divided  between  the 
furnace  and  ladle.  For  this  reason  it  is  necessary  to  make 
allowances  for  such  losses  when  calculating  the  necessary 
dose.  Further,  the  losses  are  greater  when  using  oil  for 
fuel  than  when  gas  is  used,  the  latter  flame  being  "soft"  and 
the  former  sharp.  An  oil  flame  may  be  likened  to  a  blow- 
pipe and  its  effect  always  strongly  oxidizing. 

As  already  shown,  silicon  will  reduce  the  FeO,  but  the 
reduction  is  not  always  complete,  and  what  may  escape  the 
silicon  may  further  unite  with  the  manganese.  Hence  the 
reason  for  simultaneously  using  two  powerful  and  active 
reducing  agents.  The  influence  of  the  two  agents  remaining 
in  the  finished  steel  after  their  reducing  function  will  be 
considered  later. 

The  yield  of  metal  after  conversion  against  the  weight 
charged  is  a  variable  one  and  depends  upon  the  character  of 
the  stock  and  manipulation.  If  the  stock,  other  than  the  pig 


MANIPULATION   OF   HEATS  IN   ACID  PRACTICE  49 


iron,  should  be  of  light,  thin  sections,  there  will  be  a  heavy 
melting  loss  due  to  excessive  burning  or  oxidizing.  If  the 
flame  should  be  very  sharp  during  the  melting  period,  the 
same  condition  will  arise.  The  melting  losses  are  also 
heavier  on  oil  fuel  than  on  gas  for  the  reason  stated.  Not 
only  will  the  conditions  (when  abnormal)  result  in  heavy 
melting  losses,  but  the  effect  will  be  seen  in  certain  physical 
properties  of  the  product.  That  is  to  say  "over-oxidation" 
from  any  cause  is  bad  practice;  yet  even  with  a  greater 
tendency  towards  "over-oxidation"  following  the  use  of 
oil,  the  condition  is  still  subject  to  control.  To  express  the 
losses  in  figures  to  represent  the  difference  between  metal 
charged  and  that  yielded  is  not  so  easy,  but  it  may  be  found 
to  be  about  5  per  cent. 

The  principal  points  about  the  manipulation  of  an  acid 
heat  may  be  given  as  follows : 

First — To  charge  enough  pig  iron  so  that  there  will  be  a 
high  enough  initial  carbon  to  ensure  an  easily  maintained 
fluidity  of  bath.  A  low  percentage  of  pig  iron  will  mean  a 
rapid  heat,  but  at  the  sacrifice  of  quality  and  a  very  high 
flame  temperature.  The  less  carbon  charged  the  greater 
the  chances  of  over-oxidation. 

Second — Charge  as  heavy  sections  of  scrap  as  possible 
and  protect  it  as  far  as  possible  from  burning  with  a  cov- 
ering of  pig  iron. 

Third — Watch  the  flame  conditions,  to  guard  against  un- 
due burning  of  stock.  This  point  calls  for  a  high  degree  of 
skill  to  maintain  flame  conditions  and  yet  reach  the  thermal 
ranges  necessary  to  melt  the  stock. 

Fourth — Be  judicious  in  oreing  heats.  Too  much  ore  is 
harmful. 

Fifth — Aim  for  uniformity  of  product  in  a  given  class  of 
work. 

Sixth — Over-anxiety  for  tonnage  will  make  the  scrap  pile 
grow. 


CHAPTER  V 


BASIC  PRACTICE — SLAG — SILICON — SULPHUR — PHOS- 
PHORUS— MANGANESE — CARBON — SLAG  COM POSI- 
TION— ORDER  OF  CHARGING — MELT- 
ING— CHARGING  COLD  STEEL 


The  problem  of  charging  into  a  basic  open-hearth  fur- 
nace, phosphoritic  and  otherwise  impure  materials,  convert- 
ing the  same  into  good  castings,  offers  many  interesting 
features.  To  get  satisfactory  and  uniform  results,  certain 
conditions  require  close  attention  and  niceties  of  adjustment- 
When  with  a  suitably  lined  basic  hearth  and  the  proper 
melting  stock  it  is  possible  to  begin  with  a  high  initial  phos- 
phorus and  sulphur  content  and  end  with  an  almost  com- 
plete removal  of  them,  it  is  clear  that  the  chemical  history  of 
the  manipulations  in  conversion  is  more  varied  than  that  of 
an  acid  heat.  As  already  stated,  95  per  cent  of  the  phos- 
phorus and  60  per  cent  to  75  per  cent  of  the  sulphur  can  be 
eliminated  in  a  basic  bottom.  Concerning  the  other  con- 
stituents the  conditions  in  regard  to  their  removal  during 
conversion  and  their  presence  in  the  finished  product  are 
practically  the  same  as  in  acid  castings. 

SLAG 

Given,  then,  a  basic  bottom  and  melting  stock,  the  changes 
in  a  heat  will  be  considered.  The  function  of  the  basic  bot- 


MANIPULATION  OF  HEATS  IN   BASIC   PRACTICE  51 

torn  is  only  a  refractory  one  and  the  material  entering  into 
it  plays  no  part  in  the  direct  purification  and  conversion  of 
the  stock.  The  calcerous  slag  is  the  active  agent  and  the 
bottom  must  be  of  such  material  that  the  action  of  such  a 
slag  will  have  the  least  possible  cutting  effect.  To  mini- 
mize that  effect,  the  best  results  will  be  obtained  with  a  mag- 
nesite  lining  prepared  as  previously  described.  Limestone 
or  calcium  carbonate  forming  the  slag  and  classified  as  a 
"base"  will  not  flux  with  magnesite,  also  a  "base."  That  is, 
an  admixture  of  two  or  more  bases  will  successfully  resist 
high  temperature  or  those  common  to  steel  melting;  but  a 
combination  of  an  acid  (silica,  etc.)  and  a  base  (lime  or 
magnesite,  etc.)  will  at  similar  ranges  of  temperature  read- 
ily fuse.  Hence  the  metallurgical  necessity  of  the  hearth 
lining  being  of  a  similar  character  chemically  to  that  of  the 
slag  which  may  be  formed  in  open-hearth  melting. 

Silica  being  greedy  for  any  base  and  always  ready  to 
fuse  in  the  presence  of  a  base,  the  life  of  a  basic  hearth 
will  be  subject  to  its  influence,  therefore  it  is  important  that 
the  substance  be  allowed  to  enter  the  charge  only  in  the 
smallest  amounts  possible.  Through  the  charge  it  will  be 
carried  in  as  silicon  (subsequently  changed  to  silica)  and 
sand  adhering  to  the  stock.  With  pig  iron  cast  in  chills, 
the  amount  of  sand  from  that  source  will  be  practically  nil. 
Defective  castings  charged  directly  from  the  molding  floor 
may  have  more  or  less  sand  on  them  and  unless  they  are 
carefully  cleaned  to  free  them  from  burnt  cores,  etc.,  there 
will  be  danger  of  undue  hearth  scorification  both  on  the 
slag  line  and  bottom,  causing  an  increased  use  of  refrac- 
tories for  patching. 

SILICON 

Theoretically  silica  or  silicon  should  be  absent  in  basic 
stock.  Practically  it  is  not  free  from  either,  but  the  condi- 
tion is  none  the  less  subject  to  control.  Therefore  in  se- 
lecting pig  iron  for  basic  melting  the  maximum  percentage 


52  MANIPULATION  OF  HEATS  IN  BASIC  PRACTICE 


of  silicon  is  given  as  one  per  cent.  The  amounts  of  that 
element  in  the  various  kinds  of  steel  scrap  are  so  low  that 
the  figures  are  negligible.  Assuming  the  total  charge  to 
be  equal  parts  of  pig  iron  and  steel  scrap  the  initial  silicon 
carried  in  by  stock  will  average  about  0.5  per  cent.  It  is 
good  practice  to  keep  in  the  neighborhood  of  that  figure, 
but  a  slight  variation  or  increase  will  not  be  a  serious  ob- 
jection. If  there  should  be  on  hand  some  "off  basic  pig 
iron"  that  is  high  in  silicon  (over  one  per  cent),  or  high  in 
sulphur  (over  0.05  per  cent),  a  small  quantity  can  be 
charged  at  the  rate  of  about  one  per  cent  of  the  charge  and 
will  have  but  a  very  slight  effect  upoij  the  desired  initial 
composition. 

SULPHUR 

In  regard  to  sulphur  and  its  position  in  the  composition 
of  the  charge,  it  does  not  seem  necessary  to  be  very  rigid 
as  to  how  much  can  be  considered  dangerous.  Actually 
standard  basic  pig  iron,  while  rated  at  0.05  per  cent  maxi- 
mum carries  more  than  that  because  of  the  generally  ac- 
cepted method  of  analysis  giving  uniformly  low  results. 
Were  a  more  tedious  method  and  a  more  accurate  one  em- 
ployed, the  figures  on  sulphur  would  generally  be  nearer 
0.07  per  cent  than  the  standard  stock  requirements;  hence 
the  amount  of  sulphur  actually  going  into  a  charge  is  really 
higher  than  shown  by  the  individual  analyses  of  the  pig 
irons  forming  part  of  it.  The  same  differences  between 
the  apparent  analyses  and  actual  content  of  sulphur  holds 
true  on  various  grades  of  pig  iron  until  very  low  amounts 
are  reached.  In  the  light  of  recent  practice,  the  influence 
of  sulphur  in  the  finished  product  is  not  regarded  as  harm- 
ful as  it  once  was.  There  is  therefore  no  good  reason  to 
place  a  strict  limit  on  how  much  shall  go  into  a  charge.  On 
an  average  the  total  amount  will  rarely  go  above  0.04  per 
cent.  Rail  scrap  frequently  carries  0.07  per  cent  and  over. 
The  pig  iron  will  range  from  o.oi  to  0.05  per  cent,  and 


MANIPULATION    OF    HEATS    IN    BASIC    PRACTICE  53 


with  many  kinds  of  steel  scrap  to  select  from,  ranging  from 
0.02  per  cent  and  higher,  it  will  not  be  difficult  to  keep  the 
initial  sulphur  at  or  about  the  average  stated  if  so  desired. 
In  the  writer's  experience  there  was  a  time  when  it  was 
considered  bad  practice  to  have  the  initial  sulphur  exceed 
0.03  per  cent,  and  the  aim  was  to  get  lower.  (At  this  point 
the  question  as  to  the  influence  of  sulphur  will  not  be  con- 
sidered, but  will  be  deferred  to  a  subsequent  chapter). 
With  a  normal  basic  slag  and  proper  conditions,  much 
higher  ranges  of  initial  sulphur  can  be  safely  handled. 
There  will  be  almost  complete  elimination  in  conversion,  so 
that  specification  for  finished  product  can  be  kept  within 
easy  reach  even  with  an  initial  sulphur  of  0.07  per  cent. 

PHOSPHORUS 

Concerning  phosphorus  and  keeping  in  mind  the  ulterior 
limit  in  the  analysis  of  the  finished  product,  it  is  as  well  not 
to  make  the  entire  pig  iron  charge  all  high  phosphorus 
material.  While  the  figure  on  standard  basic  pig  iron  is 
one  per  cent  and  was  drawn  for  ingot  practice  for  castings 
it  is  better  to  have  at  least  two  kinds  of  basic  pig  of  which 
one  may  be  low  and  one  other  standard.  A  brand  carry- 
ing about  0.25  per  cent  of  phosphorus  or  less  is  not  diffi- 
cult to  procure.  With  a  charge  of  mixed  brands  of  pig 
iron,  and  the  usual  varieties  of  scrap,  it  will  be  possible 
to  keep  the  initial  phosphorus  of  the  charge  low.  During 
the  progress  of  conversion  and  with  a  strongly  basic  slag, 
there  will  be  practically  a  total  absorption  of  phosphorus 
by  it  from  the  bath.  At  the  end  of  the  heat  in  recarburizing 
with  ferro-silicon,  etc.,  there  will  be  a  tendency  on  the  part 
of  the  phosphorus  to  re-enter  the  metal,  depending  in  a 
great  measure  upon  the  amount  of  that  element  charged, 
and  the  basicity  of  the  slag.  There  is  always  some  re-ab- 
sorption, and  it  is  greater  with  all  high  phosphorus  pig 
than  when  it  may  be  diluted  with  low  phosphorus  pig  iron. 
Hence  the  need  of  mixing  the  pig  iron  in  regard  to  phos- 


54  MANIPULATION    OF    HEATS    IN    BASIC    PRACTICE 

phorus  content.  Average  practice  will  give  a  negligible 
reabsorption  if  the  initial  phosphorus  is  about  o.i  to  0.3 
per  cent. 

MANGANESE 

In  addition  to  the  elements  enumerated,  there  is  always 
more  or  less  manganese  carried  in  with  the  stock.  In 
basic  melting  it  is  useful  in  several  ways.  One  function 
is  to  assist  in  maintaining  a  necessary  fluidity  of  the  slag, 
and  it  will  exist  in  that  body  principally  as  an  oxide,  re- 
sulting from  the  metal  in  the  charge.  It  also  aids  in  the  re- 
moval of  sulphur  in  the  bath,  and  at  some  period  during  the 
melting  unites  with  it,  forming  a  readily  fusible  sulphide 
of  manganese  which  floats  upwards,  and  either  dissolves 
in  the  slag  or  upon  reaching  the  surface  and  becoming  ex- 
posed to  the  flame  action,  may  be  oxidized  or  volatilized. 
The  action  of  manganese,  however,  is  not  quite  clear,  but 
from  actual  results  there  is  no  doubt  that  its  influence  in 
de-sulphurizing  is  quite  potent.  In  that  respect  it  operates 
in  conjunction  with  the  Ca  O  (lime)  furnished  by  the  lime- 
stone, which  is  also  an  active  de-sulphurizer.  It  has  been 
observed  that  a  moderately  high  initial  manganese  assists 
in  washing  the  bath  of  dissolved  oxides  always  present  in 
metal  which  has  been  subject  to  the  impinging  action  of 
the  flame  before  the  period  of  liquation  has  been  reached 
and  the  mass  disappears  below  the  slag.  The  deoxidizing 
effect  will  not  begin  until  the  mass  has  partially 
or  entirely  fused  and  is  .  covered  with  a  layer  of 
slag.  Deoxidizing  will  take  place  by  the  union 
of  silicon  and  carbon  with  the  oxygen,  and  what- 
ever manganese  may  be  present  in  excess  of  that 
which  may  unite  with  the  sulphur  will  considerably  aug- 
ment the  effect.  The  joint  operation  of  the  three  elements 
will  give  cleaned  metal.  With  ordinary  melting  stock  the 
average  or  initial  manganese  will  be  about  0.5  per  cent,  but 
if  it  is  possible  by  the  use  of  a  high  manganese  pig  iron  to 


MANIPULATION    OF    HEATS   IN    BASIC   PRACTICE  55 

raise  it  nearer  one  per  cent,  the  results  or  deoxidizing  ef- 
fect will  be  more  satisfactory.  Or  in  the  absence  of  that 
kind  of  melting  stock,  the  deficiency  can  be  made  up  with 
spiegeleisen,  an  alloy  carrying  20  per  cent  of  manganese 
or  a  certain  amount  of  manganese  ore  will  be  useful  for  the 
same  purpose,  if  charged  at  the  proper  time, — before  the 
first  portion  of  metal.  It  is  recommended,  however,  that 
the  needed  manganese  be  carried  in  by  high  manganese  pig 
iron,  because  it  is  possible  to  get  a  better  distribution  of 
that  element  than  by  adding  a  small  quantity  of  the  alloy 
mentioned  to  make  up  any  deficiency.  For  that  reason  it 
is  good  practice  when  purchasing  melting  stock,  to  have  on 
hand  pig  iron  carrying  between  1.5  to  2.5  per  cent  man- 
ganese. 

CARBON 

Since  pig  iron  generally  contains  2.5  to  3.5  per  cent  total 
carbon  and  with  50  per  cent  pig  and  50  per  cent  steel  scrap 
the  initial  carbon  of  a  charge  will  be  from  1.5  to  2  per  cent. 
Whether  the  carbon  may  be  in  the  combined  or  graphitic 
form  is  not  considered,  because  when  the  pig  iron  is  liquid, 
it  is  all  in  the  former  condition  irrespective  of  the  constitu- 
tion before  melting.  It  will  be  observed  that  there  is  a 
difference  between  acid  and  basic  melting  in  regard  to  the 
percentage  of  pig  iron  in  the  charge.  In  the  former  there 
will  be  15  per  cent,  but  in  the  latter  50  per  cent.  The 
reason  for  the  difference  is  due  to  the  larger  volume  of  slag 
formed  in  basic  melting,  which  requires  a  considerable  por- 
tion of  the  heat  units  to  penetrate  it,  to  promote  the  neces- 
sary fluidity  of  the  bath  of  metal  below.  As  has  been 
pointed  out,  the  amount  of  carbon  present  largely  controls 
the  melting  point  of  iron  and  steel  and  with  a  high  initial 
percentage  of  it  in  a  charge  of  cold  stock,  it  is  possible  to 
acquire  liquation  at  a  relatively  low  temperature.  Were 
there  a  low  initial  carbon  as  in  acid  melting,  there  would 
be  much  trouble  with  viscosity  of  the  bath,  because  of  heat 


56  MANIPULATION   OF    HEATS    IN    BASIC    PRACTICE 


absorption  in  the  heavy  body  of  basic  slag-.  With  the  bath 
melted  at  a  high  range  of  carbon,  the  necessary  thermal 
conditions  are  comparatively  easy  to  attain.  A  high  carbon 
at  melting,  between  0.5  to  0.8  per  cent,  is  considered  good 
practice ;  further,  it  means  a  prolongation  of  that  period  in 
which  deoxidization  or  clarifying  of  the  bath  occurs.  A 
lower  carbon  at  melting  would  shorten  that  period,  and  at 
the  same  time  there  would  be  undesirable  conditions  likely 
to  arise,  such  as  low  temperature  of  the  bath,  and  overoxi- 
dized  metal,  both  tending  to  give  bad  results  in  the  product. 
Should  a  heat  melt  soft  (low  carbon)  it  can  be  "doctored" 
by  adding  cold  pig  iron,  and  the  temperature  raised  by 
flame  adjustments,  but  recourse  to  such  treatment  is  always 
dubious  as  to  the  outcome. 

SLAG    COMPOSITION 

The  foregoing  elements  of  the  charge  being  adjusted  in 
accordance  with  general  practice,  the  next  step  will  be  to 
consider  the  slag  composition,  which  is  to  play  an  impor- 
tant role  in  the  conversion  and  purification  of  the  bath.  In 
contrast  to  acid  melting,  the  slag  will  be  one  highly  charged 
with  lime,  a  substance  already  shown  to  be  objectionable 
in  an  acid  hearth,  but  desirable  in  treating  basic  stock. 
The  normal  composition  of  a  basic  slag  will  not  be  reached 
until  the  stock  has  melted  and  the  slag  attained  its  maxi- 
mum fluidity,  which  period  occurs  during  the  second  stage 
of  a  heat  that  for  convenience  may  be  designated  "Metals 
Melted."  Taking  as  an  average  the  analyses  of  twenty 
samples  of  slag  selected  from  various  normal  heats  in  the 
second  stage,  the  following  can  be  considered  the  usual 
composition  of  a  basic  open-hearth  slag: 

Silica    16.00  per  cent 

Ferrous  oxide 22.00  per  cent 

Lime    40.00  per  cent 

Magnesia    8.50  per  cent 

Manganous   oxide    8.50  per  cent 


MANIPULATION    OF    HEATS    IN    BASIC    PRACTICE  57 


The  foregoing  analysis  can  only  be  regarded  as  applying 
to  the  conditions  of  practice  existing  when  they  were  made, 
and  not  as  a  rule  to  follow  in  all  cases,  but  under  general 
conditions  they  may  serve  as  a  guide.  In  order  to  form 
a  basic  slag  there  are  several  important  conditions  to  take 
into  account.  First — Enough  lime  must  be  added  to  com- 
bine with  or  neutralize  the  silica,  which  will  result  from  the 
oxidation  of  the  silicon  carried  in  by  the  metals,  and  that 
carried  in  mechanically  as  sand ;  otherwise,  there  would  be 
a  thin  slag  and  an  undue  cutting  of  the  hearth  by  the  silica. 
Second — Too  much  lime  must  be  avoided,  as  it  tends  to 
form  a  thick,  pasty  slag  that  causes  trouble  in  tapping  the 
furnace  or  brings  about  a  heavy  consumption  of  fluorspar 
to  flux  it. 

There  is  a  medium  to  be  sought  between  basicity  and 
fluidity  and  at  the  same  time  the  function  of  the  slag  in  ab- 
sorbing and  retaining  phosphorus  must  not  be  overlooked. 
The  measure  of  the  latter  action  mainly  depends  upon  the 
amount  of  lime  in  excess  of  that  united  with  the  silica,  lime 
in  a  basic  slag  being  the  active  de-phosphorizing  agent. 
As  to  fluidity,  that  condition  in  addition  to  the  influence 
of  silica  will  depend  upon  the  varying  amounts  of  man- 
ganese in  the  stock  which  enters  the  slag  as  an  oxide.  Ox- 
ide of  iron  operates  in  the  same  manner  and  is  always  pres- 
ent independently  of  that  added  as  iron  ore.  The  iron 
oxide  of  the  slag  will  result  from  the  rusty  coating  on  the 
stock  and  the  impinging  action  of  the  flame  during  the  first 
stages  of  a  heat.  In  general  terms  the  higher  the  content 
of  silica  the  greater  the  fluidity,  but  at  the  expense  of  de- 
phosphorization  and  hearth.  Fortunately  the  medium  can 
be  found  because  of  the  presence  of  iron  and  manganous 
oxide,  since  a  law  seems  to  exist  in  slag  formations  that 
fluidity  or  fusibility  is  controlled  by  the  number  of  bases 
present.  So,  assisted  by  manganous  oxide  and  iron  oxide 
in  the  presence  of  lime  and  silica,  desirable  slag  conditions 
in  basic  melting  can  be  attained  without  much  difficulty. 

In  addition  to  the  elements  given  in  the  slag  analysis 


58  MANIPULATION   OF    HEATS    IN    BASIC    PRACTICE 


there  may  be  small  negligible  quantities  of  alumina  and 
alkalies.  The  amount  of  magnesia  results  mainly  from 
hearth  cutting.  To  forecast  the  exact  amount  of  lime  to 
be  added  solely  on  theoretical  grounds  is  not  easy,  because 
the  total  available  silica  cannot  be  accurately  determined 
owing  to  the  uncertain  quantity  of  sand  adhering  to  the 
stock.  Whatever  silica  may  be  available  in  the  stock  will 
require  at  least  enough  lime  in  the  ratio  of  I  to  3  to  satisfy 
it.  Also  the  purity  of  the  limestone,  generally  used  as  a 
carrier  for  the  necessary  lime  of  the  slag,  must  be  taken 
into  account  and  any  silica  this  may  have  will  depreciate 
the  available  lime  in  the  same  degree.  Therefore,  the  near- 
er a  limestone  approaches  a  pure  carbonate  of  lime  the 
greater  its  efficiency.  In  actual  practice  the  amount  of 
limestone  required  to  form  a  normal  slag  will  vary  between 
7  and  15  per  cent  of  the  weight  of  the  charge.  With 
standard  melting  stock  and  a  pure  limestone  it  will  be  com- 
paratively easy  to  get  satisfactory  adjustments.  In  the 
hands  of  a  skillful  operator  assisted  by  the  chemist  the  be- 
havior of  a  heat  can  be  followed  at  any  desired  stage,  so 
that  untoward  conditions  of  purification  will  be  within 
control.  Agencies  are  constantly  at  work  in  slag -forma- 
tions following  the  laws  of  attractions  and  affinities  which 
present  problems  of  scientific  interest.  To  solve  their  com- 
plexities would  be  a  difficult  task. 

If  an  open-hearth  furnace  be  regarded  as  a  chemist's 
laboratory  experiment  on  a  large  scale,  and  viewed  from 
a  chemist's  standpoint,  the  delicacies  of  definite  chemical 
reactions  are  not  obliterated  because  of  the  very  hugeness 
of  a  furnace.  Whether  the  operation  be  conducted  on  a 
minute  scale  or  on  a  larger  one,  definite  laws  are  omni- 
present. Could  the  operator  bear  in  mind  that  he  is  hand- 
ling tons  of  material  with  forces  equally  potent  as  in  the 
chemist's  ounces,  he  would  stand  in  awe  of  them.  Careful, 
intelligent  work  combined  with  practical  experience  makes 
it  possible  to  put  basic  practice  in  the  same  plane  of  effi- 


MANIPULATION   OF  HEATS  IN  BASIC   PRACTICE  59 

ciency  as  acid  melting  notwithstanding  prejudice  to  the 
contrary  existing  in  some  minds. 

ORDER   OF    CHARGING 

Having  determined  upon  the  amount  of  limestone  neces- 
sary to  form  the  basic  slag,  the  next  step  will  be  to  consider 
the  order  of  charging.  With  a  basic  hearth  prepared  as 
outlined  in  previous  chapters  the  method  of  charging  may 
be  conducted  as  follows :  First  the  stone  is  spread  over  the 
bottom  in  as  regular  layers  as  possible,  followed  by  the 
lighter  sections  of  scrap,  which  should  be  more  or  less 
rusted.  If  not  rusty,  some  iron  ore  may  be  added  with 
the  scrap  to  make  up  the  lack  of  oxide  to  assist  in  subse- 
quent slag  fusibility.  Then  two-thirds  of  the  pig  iron 
should  be  distributed  as  evenly  as  possible,  which  may  be 
followed  by  the  remainder  of  the  scrap.  By  this  time  the 
furnace  will  be  well  filled  with  bulky  stock,  and  it  may  be 
necessary  to  allow  the  flame  to  partly  melt  it,  thus  forming 
room  for  the  final  addition  of  pig  iron. 

The  serious  part  of  melting  now  begins  and  at  this  stage 
the  finished  product  in  regard  to  quality  will  be  greatly  in- 
fluenced by  the  manner  in  which  the  exposed  stock  may  be 
subjected  to  flame  action.  There  will  be  a  desire  on  the  part 
of  the  operator  to  get  the  heat  out  of  the  furnace  in  record 
time  and  with  speed  in  mind  the  temptation  to  use  a  sharp, 
hot  flame  will  be  strong.-  On  the  other  hand,  a  soft,  mellow 
flame  will  not  melt  as  quickly  as  a  sharp  one,  yet  the  char- 
acter of  the  product  will  be  better  than  under  the  first 
named  conditions.  In  one  instance  the  bath  will  be  highly 
charged,  when  melted,  with  dissolved  oxides  and  in  the 
other  instance  less  so.  It  is  not  possible  under  any  condi- 
tions to  melt  a  mass  of  pig  iron  and  steel  scrap  without 
some  formation  of  oxides,  and  their  subsequent  solution 
in  the  bath,  so  long  as  it  remains  uncovered  by  a  protective 
layer  of  slag.  Good  practice  requires  that  there  be  a  divid- 
ing line  between  speed  and  slowness,  a  sharp  flame  and  a 


6O  MANIPULATION    OF    HEATS    IN    BASIC    PRACTICE 


soft  one,  and  that  object  is  a  difficult  one  to  reach.  The 
quantitative  expression  of  dissolved  oxides  cannot  be 
stated,  but'  their  influence  can  be  detected  in  varying  de- 
grees. That  such  conditions  do  exist  is  a  fact,  and  the  con- 
clusion is  based  upon  careful  observations  and  research, 
the  results  pointing  undoubtedly  to  the  influence  of  the 
flame  action,  whether  gas  or  liquid  fuel  may  be  used  and 
also  to  the  amount  of  initial  carbon  present  in  the  stock. 
Oreing  during  the  second  stage  or  "Metals  Melted"  also 
may  aggravate  the  evil.  That  it  is  an  evil,  will  be  pointed 
out,  and  one  not  fully  appreciated  or  understood.  To  it 
can  be  traced  the  non-success  and  consequent  prejudice 
against  basic  melting,  because,  in  some  instances,  it  has  been 
found  in  certain  physical  requirements  that  basic  steel  was 
not  as  good  as  acid  steel  for  castings.  In  other  words,  ex- 
pressing the  difference  between  basic  and  acid  steel  in 
regard  to  certain  physical  properties,  basic  steel  is  more 
likely  to  carry  dissolved  oxides  than  acid  steel,  provided 
care  has  been  taken  to  guard  against  their  introduction  or 
formation.  Differences  in  chemical  composition  can  only 
exist  in  the  amount  of  sulphur  and  phosphorus  for  a  given 
grade  of  product  and  the  said  differences  being  too  small 
to  exert  any  great  influence,  no  cause  can  be  assigned  other 
than  the  one  mentioned  in  studying  the  contrasting  physi- 
cal properties  of  both  classes  of  steel.  The  condition  of 
over-oxidation  is  not  so  liable  to  present  itself  with  a  gas 
flame,  but  even  such  a  flame  can  be  so  adjusted  as  to  abuse 
the  stock.  With  an  oil  flame  the  danger  is  greater,  because 
of  the  intense  blow  pipe  effect  of  the  oil  burner.  In  ex- 
perienced hands,  however,  quality  duly  regarded,  normally, 
the  oxidizing  effect  with  any  kind  of  fuel  need  not  be  ex- 
cessive. 

MELTING 

Under  flame  action  in  a  fully  charged  furnace  the  stock 
will  soon  begin  to  melt  and  it  will  be  observed  that  the  melt- 


MANIPULATION    OF   HEATS    IN    BASIC    PRACTICE  6l 


ing  of  the  pig  iron  goes  on  quite  rapidly,  dripping  to  the 
hearth  in  small  streams,  while  the  steel  scrap  melts  at  a 
slower  rate,  and  in  melting,  the  liquid  steel  frequently  scin- 
tillates or  burns  forming  either  vapors  or  solid  oxide. 
The  dripping  pig  iron  lessens  that  action,  more  or  less,  by 
protecting  the  lower  carbon  steel  stock.  The  melting  pro- 
ceeds gradually,  and  the  mass  decreases  in  bulk  and  passed 
below  a  layer  of  rapidly  forming  slag.  At  this  time,  how- 
ever, the  slag  formation  is  not  entirely  complete,  but  will 
be  found  to  consist  mostly  of  silica  and  iron  oxide  with 
comparatively  little  lime,  the  temperature  of  the  furnace 
at  this  point  not  being  sufficiently  high  to  thoroughly  dis- 
solve the  lime  still  resting  on  the  bottom  of  the  furnace. 
The  composition  of  the  slag  at  this  period  is  practically 
an  acid  one  and  results  from  the  sand  of  the  stock  and  the 
silicon  of  the  metals,  since  it  is  one  of  the  first  elements  to 
submit  to  oxidation.  Samples  taken  from  the  first  portions 
of  melted  metal  have  shown  a  high  sulphur  content,  much 
higher  than  that  carried  in  by  the  stock.  The  cause  can  be 
attributed  to  the  absorption  of  sulphur  from  the  flame. 
During  the  first  stage  but  little  information  can  be  ascer- 
tained as  to  the  changes  which  may  take  place  in  the  com- 
position, because  the  mass  is  a  conglomeration  of  pasty 
semi-liquid  pig  iron,  steel  and  slag. 

CHARGING  COLD  STOCK 

In  charging  cold  stock  about  one  half  of  the  time  re- 
quired to  work  a  fifteen  to  a  twenty-ton  heat  is  taken  up 
in  melting.  As  that  interval  advances  the  slag  is  increasing 
in  volume  and  some  changes  in  composition  will  take  place 
in  the  first  portions  of  the  metals  melted.  The  slag  is  more 
or  less  viscous  with  lumps  of  lime  coming  to  the  surface 
as  it  becomes  loosened  from  the  bottom.  There  is  a  foam- 
ing or  bubbling  in  the  slag  caused  by  COa  being  liberated 
from  the  limestone  and  also  by  the  action  between  the  ox- 
ides of  the  slag  and  the  carbon  of  the  bath.  As  the  lime 


62  MANIPULATION    OF   HEATS   IN    BASIC    PRACTICE 


continues  coming  to  the  surface  it  increases  the  basicity  of 
the  slag  and  with  that  condition  there  will  be  a  rapid  ab- 
sorption of  phosphorus  from  the  bath. 

The  operator  feels  over  the  bottom  of  the  furnace  with 
a  long  bar  to  determine  whether  the  bath  is  entirely  melted 
or  not.  If  no  pasty  masses  are  touched  the  bath  is  com- 
pletely molten.  A  sample  of  metal  is  then  poured  into  a 
small  oblong  mold,  quenched  and  broken  to  study  the  frac- 
ture, the  appearance  of  which  indicates  the  carbon  present 
and  also  whether  there  may  be  any  phosphorus  remaining. 
An  experienced  eye  can  readily  read  the  carbon  of  the  test 
quite  closely.  If  the  grain  is  small  and  the  fracture  of 
rather  a  dull  color,  the  heat  is  said  to  have  melted  "hard." 
If  the  grains  are  large  and  bright  the  heat  has  melted 
"soft."  Other  indications  confirm  this  in  the  way  the  first 
test  piece  may  break  under  the  blows  of  a  sledge,  the 
"hard"  or  high  carbon  steel  snapping  easily,  while  the 
"soft"  or  low  carbon  steel  bends  or  flattens  before  fracture. 

To  confirm  the  melter's  judgment,  as  a  rule,  the  first  test 
piece  is  sent  to  the  laboratory  for  a  quick  test  on  carbon 
and  phosphorus.  When  the  test  piece  indicates  a  high 
carbon,  the  melter  does  not  wait  for  the  analysis,  which 
only  occupies  about  ten  minutes,  but  may  throw  into  the 
bath  a  few  shovels  of  iron  ore  to  assist  in  the  lowering 
of  the  carbon,  and,  at  the  same  time,  thin  the  slag.  In  a 
few  moments  the  chemist  reports  carbon  usually  0.50  to 
0.70  with  only  a  trace  of  phosphorus.  The  melter  is  now 
satisfied  that  his  conditions  are  normal.  Should  the  phos- 
phorus have  shown  incomplete  removal  in  the  first  test,  a 
second  one  would  be  taken  after  an  interval  of  about  fif- 
teen minutes  and  submitted  to  another  chemical  analysis. 
The  addition  of  the  iron  ore  immediately  after  the  first  test 
would  have  increased  the  slag's  basicity  and  fluidity  and 
no  doubt  would  have  eliminated  what  phosphorus  might 
have  remained  in  the  bath  at  the  time  of  the  first  sample. 
Usually  the  second  test  shows  phosphorus  out  of  harm's 
way. 


MANIPULATION    OF   HEATS    IN    BASIC    PRACTICE  63 


If  the  phosphorus  resists  removal,  it  is  necessary  to  add 
lime  to  the  slag.  This  would  have  a  tendency  to  cool  the 
bath  and  also  raise  the  lime  content  of  the  slag  and  of 
course  intensify  the  de-phosphorizing  action.  If  the  tem- 
perature of  the  bath  at  melting  be  very  high,  there  may  be 
a  tendency  to  retard  the  removal  of  phosphorus,  since  there 
seem  to  be  certain  ranges  of  temperature  wherein  de-phos- 
phorizing does  not  depend  entirely  upon  slag  conditions. 
It  has  been  observed  that  in  cases  where  a  normal  slag  re- 
fused to  completely  de-phosphorize,  an  addition  of  a  few 
hundred  pounds  of  pig  iron  caused  a  quick  and  perfect  ab- 
sorption of  the  phosphorus  by  the  slag.  The  action  could 
only  be  explained  on  the  basis  that  the  pig  iron  so  added 
could  exert  no  other  influence  regarding  the  phosphorus 
than  that  of  cooling  the  bath.  This  fact  gives  plausibility 
to  the  theory  of  the  thermal  ranges  where  they  may  be 
a  change  or  reversal  of  affinities,  or,  in  other  words  the 
oxidizing  action  is  more  inclined  to  give  its  attention  to 
the  carbon  in  preference  to  the  phosphorus. 

The  activity  in  de-carbonizing  is  one  that  varies  with  the 
temperature  and  this  fact  also  seems  to  apply  with  equal 
force  inversely  to  phosphorus.  The  term  "very  hot"  may 
seem  indefinite  in  reference  to  the  bath  when  melted,  but 
in  the  absence  of  figures  stating  temperatures  at  the  several 
stages  of  an  open-hearth  heat,  the  use  of  vague  expressions 
concerning  them  cannot  be  avoided.  It  is  doubtful  if  the 
slight  ranges  of  temperature  covering  the  periods  affecting 
the  removal  of  phosphorus  can  be  observed  by  the  eye  even 
with  experienced  operators.  It  is  certain  that  the  ranges 
of  temperature  in  question  come  within  apparently  normal 
conditions  and  are  therefore  narrow.  But,  if  the  ranges 
were  wider,  they  would  be  readily  detected  without  the 
seeming  need  of  pyrometry  to  fix  them. 

Assuming  that  the  second  test  sample  shows  a  low  phos- 
phorus, usually  0.005 — °-OI5>  further  manipulation  proceeds 
smoothly.  The  slag  will  have  nearly  reached  its  full  share 
of  lime;  in  other  words,  the  lime  will  have  come  to  the 


64  MANIPULATION  OF  HEATS  IN  BASIC  PRACTICE 


surface  from  the  hearth  bottom  where  it  was  charged.  If 
the  dose  of  iron  ore  has  not  given  the  desired  fluidity  to 
the  slag,  an  addition  of  two  or  three  shovels  of  fluor-spar 
will  bring  it  about  quite  rapidly.  Fluor-spar  should  be  used 
but  sparingly  because  excessive  doses  tend  to  aggravate 
the  cutting  action  on  the  slag  line  around  the  hearth. 

If  the  first  or  second  preliminary  test  samples  show  low 
phosphorus  the  examination  for  that  element  is  not  carried 
out  in  subsequent  tests.  Only  the  carbon  is  carefully 
watched  and  after  it  has  reached  about  0.25  no  further  ore 
should  be  given  to  a  bath.  The  carbon  reduction  can  go 
on  without  any  assistance  from  that  source  because  the  slag 
will,  at  that  period,  carry  its  full  quota  of  iron  oxide  to 
actively  promote  decarburizing.  Excessive  additions  of 
iron  ore  will  surcharge  the  bath  with  oxide  \vhich  causes 
blow  holes  and  red  shortness  in  the  finished  product.  A 
liberal  use  of  iron  ore  will  shorten  the  time  of  making  a 
heat  and  in  a  measure,  increase  the  yield  of  metal  because 
the  reaction  between  the  carbon  of  the  bath  and  the  oxide 
of  iron  furnished  by  the  ore  sets  free  an  equivalent  of  metal- 
lic iron  which  enters  the  bath.  But  good  practice  demands 
discretion  in  the  treatment  of  the  bath  with  ore. 

It  generally  follows  that  when  a  heat  melts  "hard,"  tem- 
perature conditions  at  the  end  of  the  heat  will  be  normal 
because  the  initial  amount  of  carbon  will  be  high  enough  to 
produce  perfect  liquation  and  the  interval  of  time  occupied 
in  its  removal  will  be  great  enough  to  preserve  proper  ther- 
mal adjustments  by  regular  reversals  of  flame  action,  in- 
flowing air  and  outgoing  gases.  Should  a  heat  melt  "soft," 
the  temperature  of  the  bath  is  apt  to  be  low  and  without  a 
gain  in  the  carbon  much  difficulty  would  be  encountered 
with  pasty  steel.  An  attempt  to  raise  the  flame  temperature 
to  get  the  fluidity  of  the  bath  would  harm  the  roof  and 
brick  work  of  furnace  by  scorching.  But  recourse  is  had 
to  extra  doses  of  cold  pig  iron  to  furnish  the  necessary  car- 
bon and  thus  promote  fusion  and  other  desirable  conditions. 
Such  practice  is  called  "doctoring"  but  the  outcome  is 


MANIPULATION    OF    HEATS    IN    BASIC    PRACTICE  65 


never  so  satisfactory  as  when  the  heat  is  worked  naturally. 
It  is  a  safe  rule  that  when  a  heat  melts  "soft"  and  conse- 
quently dull  or  cold,  that  the  first  preliminary  test  will 
show  thorough  slag  absorption  of  phosphorus.  This  fact 
gives  plausibility  to  the  theory  of  the  temperature  ranges 
affecting  the  removal  of  that  element. 

When  the  carbon  reaches  a  point  where  the  test  samples 
are  very  tough,  difficult  to  break  and  showing,  upon  frac- 
ture, a  fibrous  structure,  and  chemical  tests  show  them  to  be 
between  o.io  to  0.14  carbon,  preparations  are  made  to  finish 
the  heat.  If  a  test  spoon  of  liquid  steel  be  taken  from  the 
bath  and  poured  over  the  lip,  running  freely  and  leaving 
the  spoon  clean  and  free  from  skull  or  chilled  steel,  the  tem- 
perature of  the  bath  is  considered  good.  The  next  step  will 
be  to  quiet  the  bath  by  adding  one-third  of  a  weighed  por- 
tion of  ferro-manganese.  This  material  as  shown  in  pre- 
vious chapters  takes  precedence  over  the  remaining  carbon 
in  de-oxidizing  and  so  lessens  the  ebullition  of  gaseous  car- 
bon. After  an  interval  of  a  few  minutes  the  heat  of  metal 
is  tapped  into  a  pre-heated  ladle,  and  before  the  slag  comes, 
the  final  doses  of  ferro-manganese  and  ferro-silicon  are 
thrown  in  with  the  stream  of  steel  and  the  heat  is  said  to  be 
finished.  The  furnace  bottom  is  now  drained  of  slag  and 
some  remaining  pools  of  steel.  The  slag  line  is  patched 
with  raw  dolomite  and  whatever  holes  there  may  be  in  the 
bottom  are  filled  with  ground  magnesite.  The  furnace  is 
then  ready  for  a  succeeding  charge. 


DETAILS  OF  RE-CARBURIZING 

It  will  be  noted  that  in  basic  melting  no  ferro-silicon  is 
added  to  the  bath  to  deoxidize  as  in  acid  practice.  To  do  so 
would  be  to  invite  irregularities,  such  as  a  release  of  phos- 
phorus from  the  slag,  a  re-absorption  of  it  in  the  bath,  a 
cutting  of  the  hearth,  a  great  loss  in  available  silicon  and 
uncertainty  as  to  quality  of  product.  The  measure  of  the 


66 


MANIPULATION    OF    HEATS    IN    BASIC    PRACTICE 


power  of  the  slag  to  take  up  phosphorus  from  the  bath  is 
its  basicity  and  any  addition  of  silicon  decreases  that  prop- 
erty. The  better  practice  is  to  make  the  silicon  additions 


FIG.   8. — COMPOSITION   OF   A   NORMAL  BASIC   OPEN-HEARTH   HEAT 


entirely  in  the  ladle.  If  the  ordinary  grade  of  ferro-sili- 
con  (9  per  cent  to  13  per  cent  Si)  is  used,  it  must  be  melted 
before  it  can  be  added  to  the  ladle. 


MANIPULATION    OF    HEATS    IN    BASIC    PRACTICE 


The  melting  may  be  done  in  a  small  cupola,  or  a  reverba- 
tory  furnace  fired  with  coal,  or  in  a  suitable  oil  furnace. 
In  any  case,  there  are  certain  annoyances,  such  as  hitches 
in  getting  the  ferro-silicon  melted  at  the  proper  interval 
and  in  condition  to  transfer  the  desired  quantity  to  the  steel 
ladle  when  the  heat  has  been  tapped  from  the  open-hearth 
furnace.  There  are  also  losses  in  available  silicon  due  to 
oxidation  when  melting  the  charge  of  ferro-silicon  by  any 
method.  These  losses  are  variable  and  cannot  be  avoided. 
In  making  calculations  allowances  must  be  made  for  such 
losses.  It  would  not  be  practical  to  add  the  dose  of  ferro- 
silicon,  using  the  common  grade,  cold.  The  drawbacks  just 
mentioned  can  be  avoided  by  the  higher  grade  electrolytic 
ferro-silicon  which  usually  carries  about  50  per  cent  of 
silicon.  The  quantity  of  this  latter  grade  for  a  dose  is  only 
about  one-fifth  of  the  commoner  kind,  so  that  there  is  no 
need  to  melt  it  before  using,  thus  eliminating  the  difficulties 
arising  in  handling  the  ordinary  grade.  The  heat  units 
evolved  in  the  reaction  between  the  oxide  of  iron  contained 
in  the  molten  steel  and  the  silicon  available  in  the  high 
grade  ferro-silicon,  more  than  offset  any  chilling  effect  set 
up  by  the  addition  of  a  cold  charge  of  that  material.  There 
is  always  some  consumption  of  silicon  in  de-oxidizing  and 
it  is  greater  in  basic  melting  than  in  acid.  The  loss  varies 
between  20  per  cent  to  30  per  cent  of  the  total  available, 
particularly  in  using  the  common  grade  of  ferro-silicon. 

The  greater  part  of  the  ferro-manganese  addition  can  be 
made  in  the  ladle  with  but  a  slight  loss  in  de-oxidizing  and 
with  no  chilling  effect  upon  the  liquid  steel. 

If  the  finished  product  is  to  show  a  final  analysis  as  fol- 
lows : 


C   0.20  to  0.25  per  cent 

Si    0.30  to  0.35  per  cent 

Mn    0.65  to  0.85  per  cent 


the  calculations  for  the  recarburizers,  as  an  illustration,  will 


68  MANIPULATION    OF    HEATS    IN    BASIC    PRACTICE 


be  made  on  the  basis  of  molten  FeSi  with  9  to  13  per  cent 
Si  and  also  on  FeSi  carrying  50  per  cent  Si,  the  weight  of 
the  charge  being  36,000  pounds.  Taking  the  lower  limit  of 
silicon,  in  the  final  analysis  there  will  be  required 

36,000  X  0.003  —  1 08  pounds  Si. 

With  the  ferro-silicon  averaging  n   per  cent  silicon  the 
charge  of  that  material  to  furnish  108  pounds  silicon  is 
108  X   ioo 

=  982  pounds, 

ii 

but  there  may  be  a  combined  loss  of  the  synthetical  silicon 
in  melting  and  in  de-oxidizing  of  about  20  per  cent ;  it  will 
be  necessary  to  increase  the  charge  of  ferro-silicon  accord- 
ingly to  982  X  1.2  =  1,1783/2  pounds.  The  carbon  carried 
in  by  that  quantity  will  be 

1,1783/2  X  0.015  —  17.67  or  18  pounds 
divided  by  the  weight  of  the  charge 
18 

x  ioo  =  0.04, 

36,000 
the  percentage  of  available  carbon. 

To  get  the  manganese  in  the  final  analysis  to,  say,  0.75 
per  cent  it  will  be  necessary  to  add : 
36,000  X  0.0075  ~  27°  pounds  Mn. 

Standard  ferro-manganese  carries  80  per  cent,  then  to  have 
the  synthetical  manganese  it  will  require 
270  X  ioo 

=  337//2  pounds  FeMn. 

80 

The  residual  manganese  in  the  bath  at  the  time  of  the  ad- 
ditions will  be  an  increment  and  it  will  nearly  equal  the 
loss  mentioned  in  available  manganese.  From  the  ferro- 
manganese  there  will  be  carbon  furnished  to  the  extent  of 

337^  X  0.06  =  20^4  pounds. 
21 

X  ioo  =  0.05  per  cent  C. 

36,000 


MANIPULATION    OF    HEATS   IN    BASIC   PRACTICE  69 


The  addition  of  ferro-manganese  is  divided  into  two  por- 
tions, 1-3  in  furnace  and  2-3  in  the  ladle. 

Summarizing  the  recarburizers  there  will  be  available  in 
total  elements. 

C    0.12  +          0.04          0.05          0.21 

Mn  0.15+  0.75  0.90 

Si    0.02  +  0.36  0.38 

The  foregoing  available  composition  in  regard  to  the  car- 
bon will  be  very  close  to  the  required  analysis  and  the  com- 
plete analysis  compared  with  the  total  available  elements 
will  depend  in  a  great  measure  upon  the  condition  of  the 
bath  in  regard  to  the  quantity  of  oxide  formed  during  the 
conversion  and  refining  of  the  charge. 

If  the  electrolytic  ferro-silicon  be  preferred  to  the  com- 
mon grade,  it  will  not  change  the  details  in  regard  to  the 
dose  of  ferro-manganese,  which  will  remain  the  same  as 
shown  in  the  preceding  paragraphs.  The  figures  for  sili- 
con can  be  taken  as  follows : 

36,000  X  0.003  —  1 08  pounds  Si. 
108  X  100 

=  216  pounds  Fe-Si. 

50 

"  Since  the  electrolytic  silicon  being  in  a  condensed  form 
the  de-oxidizing  effect  is  more  pronounced  and  efficient. 
The  losses  are  much  less  than  in  the  ordinary  grade.  There 
arises  no  particular  need  to  take  into  account  the  losses  or 
differences  between  the  synthetical  analysis  and  the  final. 
It  is  not  necessary  in  adding  silicon  as  a  deoxidizer  to  work 
extremely  close  to  figures  for  finished  analysis,  if  enough 
is  added  in  the  first  place  to  accomplish  the  purpose.  The 
amount  of  carbon  furnished  by  the  electrolytic  silicon  is 

0.54 

quite  small  216  X  0.0025  —  0.54  pounds  and X  IQO 

36,000 
=  o.ooi  per  cent  or  practically  nothing  at  all.     From  the 


70  MANIPULATION    OF   HEATS    IN    BASIC    PRACTICE 

ferro-manganese  there  will  be  0.05  per  cent  which  added  to 
the  residual,  assumed  to  be  0.12  per  cent,  would  make  the 
available  carbon  0.17  per  cent,  a  figure  rather  low  for 
ordinary  castings  where  the  tensile  strength  required  may 
be  60,000  to  70,000  pounds  per  square  inch. 

Two  methods  may  be  followed  to  raise  the  carbon  to 
0.20 — 0.25  per  cent.  One  is  to  finish  the  heat  at  a  corre- 
spondingly higher  residual  carbon.  The  other  is  to  make 
up  the  difference  between  0.17  and  0.20 — 0.25  by  an  addi- 
tion of  solid  carbon  in  the  form  of  coke  or  anthracite  at 
the  time  of  dosing  in  the  ladle. 

Concerning  sulphur,  there  is  no  great  effect  upon  it  at 
the  time  of  recarburizing.  The  figures  for  the  residual  and 
the  final  analyses  are  practically  the  same  excepting  occa- 
sionally a  small  decrease  coming  within  the  common  errors 
of  chemical  tests.  If  any  differences  occur  outside  of  them, 
the  lessening  of  the  sulphur  can  be  assigned  to  the  influ- 
ence of  manganese  in  combining  with  some  sulphur  and 
passing  off  into  the  slag  as  a  manganese  sulphide.  No 
gain  in  sulphur  at  this  stage  has  been  observed  in  the  writ- 
er's experience. 

If  the  initial  phosphorus  is  kept  low  in  the  charge,  about 
o.io  to  0.15  per  cent  and  with  only  0.005 — 0.015  per  cent 
remaining  at  the  time  of  finishing  the  heat,  the  synthetic 
silicon  in  the  action  of  de-oxidizing  in  the  ladle  changing  to 
silica  passes  into  the  super-natent  slag,  combines  with  the 
lime,  liberates  or  releases  some  phosphorus  held  there, 
which  immediately  reverts  to  the  molten  metal  and  raises 
the  analysis  of  that  element.  Under  such  conditions,  tak- 
ing a  sample  when  about  one-half  of  the  metal  from  the 
ladle  has  been  poured,  there  will  be  found  a  marked  in- 
crease of  the  phosphorus  over  the  residual  so  that  the 
finished  steel  will  show  0.02 — 0.03  phosphorus.  The  re- 
phosphorizing  in  the  ladle  goes  on  continually  so  long  as  the 
metal  remains  liquid  and  if  a  sample  were  taken  from  the 
last  portion  of  metal  in  contact  with  the  slag,  there  would 
be  found  a  still  further  gain  in  phosphorus.  If  a  much 


MANIPULATION    OF    HEATS    IN    BASIC    PRACTICE 


higher  initial  phosphorus  were  charged  there  would  be 
a  still  greater  revision,  and  castings  poured  at  the  end  of  a 
heat  might  be  found  with  a  content  of  phosphorus  near  the 
point  of  being  objectionable.  This  feature  of  re-absorption 
is  peculiar  to  the  basic  process  and  is  more  noticeable  in  the 
steel  castings  practice  than  in  the  production  of  ingots  for 
rolling  purposes,  because  in  the  latter  product  the  silicon 
added  at  the  end  of  a  heat  is  much  less  than  in  the  former. 
Hence  the  importance  of  not  charging  large  quantities  of 
highly  phosphoritic  stock  in  the  manufacture  of  basic  steel 
castings. 

The  melting  losses  depend  upon  the  character  of  the  stock 
and  the  conditions  of  practice  and  may  vary  from  6  per  cent 
to  12  per  cent  of  metal  charged.  In  representative  plants 
with  established  and  extensive  experience  a  yield  of  93  per 
cent  in  the  ladle  can  be  considered  a  fair  average. 


CHAPTER  VI 


CHEMICAL  ANALYSES  AND  PHYSICAL  TESTS. — DETERMINA- 
TIONS OF  SILICON,  PHOSPHORUS,  MANGANESE, 

SULPHUR  AND  CARBON  IN  STEEL  AND 
i  PIG  IRON. — PRELIMINARY 

TESTS. — PHYSICAL 
TESTS.— SOLU- 
TIONS 


The  appended  methods  of  chemical  analyses  are  the  result 
of  several  years'  experience  and  have  proven  to  be  accurate 
and  reliable.  In  several  instances,  the  methods  may  be 
considered  as  standard,  and  are  in  daily  use  in  many  lead- 
ing establishments. 

In  the  manufacture  of  basic  steel  castings,  where  it  is 
highly  important  to  know  the  extent  of  dephosphorization 
as  quickly  as  possible  in  preliminary  tests  taken  during  the 
progress  of  a  heat,  a  suitable  centrifugal  machine  is  neces- 
sary, which  can  be  purchased  through  any  house  dealing 
with  chemical  supplies. 


DETERMINATION   OF  SILICON  IN  STEEL 

Five  times  the  factor  weight  (2.3510  grams)  of  the  drill- 
ings are  weighed  off,  placed  into  a  5  %  -inch  porcelain  dish, 
and  a  watch  glass  placed  concave  side  down.  Thirty  cc. 


CHEMICAL    ANALYSES    AND    PHYSICAL    TESTS  73 


of  silicon  mixture  are  added.  The  dish  is  heated  until  the 
solution  is  evaporated,  and  fumes  of  sulphuric  acid  are 
given  off.  After  cooling,  45  cc.  hydrochloric  acid,  (i  part 
hydrochloric,  2  parts  water)  are  added.  Heat  until  all  is 
disolved,  except  the  separated  silica.  Filter,  wash  alternately 
with  hot  hydrochloric  acid  (i-i)  and  hot  water,  until  free 
from  iron  and  acid.  Burn  and  weigh.  One  fifth  the  weight 
represents  the  silicon  percentage.  Time  required,  fifty  min- 
utes. 


DETERMINATION    OF    PHOSPHORUS    IN    STEEL 

Two  grams  of  the  drillings  are  weighed  off,  placed  into 
a  250  cc.  Erlenmyer  flask,  and  35  cc.  nitric  acid  (specific 
gravity  1.2)  added.  The  flask  is  heated  until  the  drillings 
are  in  solution,  and  no  brown  fumes  are  given  off.  Ten 
cc.  of  a  five  per  cent  solution  of  potassium  permanganate 
are  added,  and  the  heating  continued  until  the  solution  is 
colored  brown,  when  a  few  drops  of  saturated  cane  sugar 
solution  are  added.  The  solution  is  cleared,  and  after  heat- 
ing a  few  minutes  the  flask  is  removed  from  the  heat,  and 
cooled  in  water.  Neutralize  with  concentrated  ammonia, 
and  acidify  with  concentrated  nitric  acid  until  the  solution 
assumes  an  amber  color.  To  this  solution  at  a  temperature 
of  70-80  degrees  Cent.,  add  50  cc.  of  ammonium  molybdate 
solution,  and  a  few  drops  of  ammonia  to  hasten  the  pre- 
cipitation. Shake  well,  and  allow  to  settle  in  a  warm  place 
for  ten  minutes.  Filter,  wash  with  cold  water  until  free 
from  acid.  Remove  paper  to  original  flask,  add  from  3  to 
5  cc.  or  more  if  necessary,  of  potassium  hydroxide  solution. 
Add  a  few  drops  of  a  one  per  cent  alcoholic  solution  of 
phenolphthalein.  Shake  thoroughly,  allow  to  stand  for  five 
minutes,  and  titrate  excess  of  alkali  with  nitric  acid  solu- 
tion. The  number  of  cubic  centimeters  of  potassium  hy- 
droxide solution,  neutralized  by  the  phosphomolybdates  rep- 
resents hundredths  per  cent  of  phosphorus  in  the  drillings. 
Time  required,  forty  minutes. 


74  CHEMICAL   ANALYSES   AND    PHYSICAL    TESTS 


DETERMINATION   OF   MANGANESE   IN   STEEL 

One-tenth  dram  of  the  drillings  is  weighed  off  and 
placed  into  a  test  tube  (i  x  8  inches),  and  15  cc.  nitric  acid 
(specific  gravity  1.2)  are  added.  The  best  tube  is  heated 
over  a  sand  bath  until  the  drillings  are  in  solution,  and  the 
nitrous  oxide  fumes  are  expelled.  About  0.7  grams  lead 
peroxide  (PbOa)  is  added  to  the  test  tube  taken  from  the 
sand  bath,  after  which  it  is  replaced  and  heated  for  one 
minute,  then  filled  two-thirds  with  hot  water.  Boil  a  few 
minutes  and  settle  by  means  of  a  centrifugal  machine. 
Pour  the  clear  solution  into  a  flask,  and  titrate  with  sodium 
arsenite  solution.  The  number  of  cubic  centimeters  of 
arsenite  solution  required,  represents  tenths  per  cent  of 
manganese  in  drillings. 

Time  required,  twenty-five  minutes. 

DETERMINATION  OF  SULPHUR  IN  STEEL 

Fifty  times  the  factor  weight  (6.88  grams)  are  weighed 
off,  and  placed  into  a  500  cc.  Erlenmyer  flask:  The  de- 
livery tube  is  attached  leading  into  a  100  cc.  Erlenmyer 
flask,  which  contains  10  cc.  hydrogen  peroxide,  10  cc. 
concentrated  ammonia,  and  20  cc.  water.  Eighty  cc.  of  hot 
hydrochloric  acid  (i-i)  are  added,  and  heat  applied. 
When  solution  is  complete,  disconnect  the  apparatus,  make 
the  solution  slightly  acid  with  hydrochloric  acid,  bring  to 
a  boil,  and  add  10  cc.  of  a  ten  per  cent  solution  of  hot 
barium  chloride.  Boil  five  minutes,  filter,  using  ashless 
pulp,  burn  and  weigh  barium  sulphate,  and  make  correction 
for  sulphur  in  hydrogen  peroxide.  The  weight  of  barium 
sulphate,  divided  by  50,  represents  thousandths  per  cent 
sulphur.  Time  required,  fifty  minutes. 

DETERMINATION  OF  CARBON  IN  STEEL 

Weigh  0.3  grams  of  drillings,  and  0.3  grams  of  stand- 


CHEMICAL    ANALYSES    AND    PHYSICAL    TESTS  75 


ard  into  separate  test  tube.  Add  5  cc.  nitric  acid  (speci- 
fic gravity  1.2).  Heat  in  a  water  bath  until  solution  is 
complete.  Cool  in  water  and  compare.  Time  required, 
thirty  minutes. 

DETERMINATION   OF   SILICON    IN    PIG   IRON 

One  gram  of  the  sample  is  washed  off  into  a  324-inch 
casserole,  and  a  watch  glass  placed  concave  side  down. 
A  few  drops  of  concentrated  hydrochloric  acid  are  added, 
then  15  cc.  of  silicon  mixture.  The  casserole  is  heated 
until  sulphuric  acid  fumes  are  given  off.  After  cooling, 
add  30  cc.  hydrochloric  acid  (1-2),  and  boil  until  all  is  dis- 
solved except  the  carbon  and  silica.  Filter,  wash  alter- 
nately with  hot  hydrochloric  acid  (i-i),  and  add  hot  water 
until  free  from  iron  and  acid;  burn  and  weigh.  If  high 
in  silicon,  treat  with  hydrofluoric  acid.  The  weight  mul- 
tiplied by  0.47  represents  the  percentage  of  silicon.  Time 
required,  one  hour. 

DETERMINATION   OF   PHOSPHORUS   IN   PIG   IRON 

From  high  phosphorus  pig  weigh  off  0.2  gram  and  from 
low  phosphorus  pig  as  much  as  is  best  suited  for  the  de- 
termination. To  the  0.2  gram  add  25  cc.  of  nitric  acid 
(specific  gravity  1.13).  Boil  until  the  drillings  are  in  so- 
lution, adding  more  acid  if  necessary.  Filter  off  graphite, 
add  potassium  permanganate,  and  proceed  as  in  the  deter- 
mination of  phosphorus  in  steel.  Time  required,  fifty  min- 
utes. 

DETERMINATION  OF  MANGANESE  IN  PIG  IRON 

Proceed  as  in  the  determination  of  manganese  in  steel. 

DETERMINATION  OF   SULPHUR  IN  PIG  IRON 

Five  grams  of  the  drillings  are  weighed  off  into  a  500 


76  CHEMICAL    ANALYSES    AND    PHYSICAL    TESTS 


cc.  Erlenmyer  flask,  and  a  delivery  tube  connected  which 
leads  into  a  glass  containing  10  cc.  cadmium  chloride  solu- 
tion, and  50  cc.  water;  70  cc.  hot  hydrochloric  acid  (i-i) 
are  added  through  the  thistle  tube,  and  heat  is  applied  until 
the  drillings  are  in  solution,  and  steam  has  driven  off  all 
other  gases.  Disconnect,  add  a  few  cubic  centimeters  of 
starch  solution,  40  cc.  hydrochloric  acid  (i-i),  and  titrate 
immediately  with  iodine  solution.  The  number  of  cubic 
centimeters  of  iodine  solution  represents  hundredths  per 
cent  of  sulphur.  Time  required,  thirty-five  minutes. 

PRELIMINARY    TESTS 

CARBON. — Weigh  off  0.2  gram  of  the  drillings,  and  0.2 
gram  of  the  standard  into  separate  test  tubes.  Heat  until 
solution  is  complete  and  compare  colors.  Time  required: 
Four  minutes. 

MANGANESE. — Proceed  as  in  the  final  test.  Do  not  boil 
after  adding  water.  Time  required,  six  minutes. 

PHOSPHORUS. — One  and  one-half  grams  of  the  steel  are 
weighed  off  into  a  300  cc.  Erlenmyer  flask,  and  35  cc.  nitric 
acid  (specific  gravity  1.2)  are  added.  When  violent  action 
ceases,  place  flask  on  heat,  boil  until  drillings  are  in  solu- 
tion and  no  brown  fumes  are  given  off.  For  every  eight 
points  carbon,  add  one  cubic  centimeter  of  concentrated 
solution  of  chromic  acid.  Boil  one  minute.  Transfer  to 
a  graduated  bulb  containing  50  cc.  molybdic  acid  solution, 
shake  violently,  and  allow  to  settle  in  centrifugal  machine. 
Each  small  division  on  bulb  represents  hundredths  per  cent 
phosphorus.  Time  required,  five  minutes. 

SOLUTIONS 
SILICON  MIXTURE: 

Water    1,300  cubic  centimeters 

Nitric  acid   435  cubic  centimeters 

Sulphuric  acid    275  cubic  centimeters 

Add  sulphuric  acid  slowly. 


CHEMICAL  ANALYSES  AND  PHYSICAL  TESTS          77 

STANDARD  ACID  AND  ALKALI  FOR  PHOSPHORUS  DETERMI- 
NATION : 

i  per  cent  solution  potassium  hydroxide, 
i  per  cent  solution  nitric  acid. 

100  milligrams  oxalic  acid  crystals  equals  10  cc.  potas- 
sium hydroxide. 
Standardize  with  steel  of  known  phosphorus  contents. 

MOLYBDATE  SOLUTION: 

Stock  Solution. 

Molybdic  acid  250  grams 

Ammonia  1,000  cubic  centimeters 

To  use,  90  cc.  stock  solution  in  338  cc.  nitric  acid  1.20 
specific  gravity. 

Keep  acid  cool,  and  stir  while  adding  molybdic  acid. 

SODIUM  ARSENITE  SOLUTION  : 
STOCK  SOLUTION. 

Sodium    Carbonate    15  grams 

Arsenous    Oxide    5  grams 

Water    500  cubic  centimeters 

Boil  and  filter. 

To  use,  take  68  cc.  stock  solution  to  2,000  cc.  water, 
standardize  against  steel  of  known  manganese  contents. 

CADMIUM  CHLORIDE  SOLUTION: 

Cadmium  chloride  35  grams 

Water    1,200  cubic  centimeters 

Ammonia    800  cubic  centimeters 

IODINE  SOLUTION: 

Iodine    9  grams 

Potassium  Iodide    18  grams 

Dissolve  in  a  few  cc.  of  water  and  dilute  to  two  liters. 
Standardize  against  American  Foundrymen's  Association 
pig  iron  standards. 


CHEMICAL    ANALYSES    AND    PHYSICAL    TESTS 


STARCH  SOLUTION: 

Mix  a  tablespoon  full  of  starch  with  a  little  cold  water, 
and  pour  into  100  cc.  of  boiling  water,  and  continue  the 
boiling  for  some  time.  Shake  before  using. 

NITRIC  ACID,  SPECIFIC  GRAVITY,  1.2: 

Nitric  acid   1,250  cc. 

Water    185  cc. 

NITRIC  ACID,  SPECIFIC  GRAVITY,  1.13: 

Nitric  acid   645  cc. 

Water    1,800  cc. 

PHYSICAL   TESTS 

The  specifications  prepared  by  the  American  Society  for 
Testing  Materials,  and  shown  in  the  following  table,  are 


FIG.    9. — STANDARD    TEST    BAR 

quite  generally  recognized  as  being  fair  to  both  producer 
and  customer.  An  objection  to  be  raised  is  the  costly 
style  of  the  test  bars  recommended  (Fig.  g). 


CHEMICAL   ANALYSES    AND   PHYSICAL    TESTS  79 


When  a  large  number  of  tests  are  to  be  made  in  the  ma- 
chine, cutting  the  threads  greatly  increases  the  cost. 

When  no  specifications  for  physical  tests  are  imposed 
the  type  of  the  bar  shown  in  Fig.  10,  will  answer  for  works 


FIG.     10. — TEST    BAR    FOR    WORKS*    TEST 

tests,  solely  as  a  guide  to  the  quality  of  product,  and  where 
the  customer  does  not  insist  upon  the  test-bar  with  the 
threaded  ends  as  illustrated. 

The  specifications,  mainly,  are  drawn  to  cover  the  physical 
properties  and  they  alone  should  be  considered,  for  the  rea- 
son that  there  is  no  distinct  relation  between  the  chemical 
composition  and  the  physical  behavior. 

The  method  of  the  treatment  of  castings  is  the  prime 
consideration,  and  with  a  given  chemical  composition,  it  is 
possible  to  get  a  wide  variation  in  physical  tests  with  dif- 
ferent heat  treatments.  From  the  standpoint  of  the  manu- 
facturer, specifications  should  only  be  applied  to  physical 
tests,  leaving  to  him  the  adjustments  of  the  processes  of 
manufacture  to  harmonize  with  the  expected  physical  re- 
quirements. 

Test  bars  can  only  at  best,  show  the  condition  their 
metal  may  be  in,  both  in  regard  to  the  composition  and  the 
treatment  to  which  they  may  have  been  subjected. 

It  would  not  follow  that,  because  a  test  bar  represent- 
ing a  given  heat  of  steel,  gives  poor  results  in  tensile  or 
bending  stress,  the  entire  heat  was  poor  also  in  that.  A 
test-bar  can  only  show  what  might  be  expected  of  a  finished 
casting  of  equal  composition  if  it  were  to  receive  the  same 
treatment  as  did  the  bar. 

Tensile  and  bending  tests  serve  useful  purposes,  but  still 


80  CHEMICAL    ANALYSES    AND    PHYSICAL    TESTS 


leave  something  lacking.  If  a  test-bar  under  such  stress 
gives  excellent  results  or  if  a  finished  casting  be  subjected 
to  the  drop  test,  and  possibly  bends  without  fracture,  prov- 
ing great  ductility,  the  evidence  is  not  necessarily  a  posi- 
tive guide  as  to  life  in  service.  Quite  generally  a  steel  cast- 
ing is  set  up  in  service  in  such  a  manner  that  it  may  be 
constantly  under  alternating  stresses  or  rapid  and  repeated 
shocks.  Practical  results  from  service  data  do  not  con- 
firm the  theory  that  ductile  steel  should  resist  such  strains. 
Failures  under  such  stresses  frequently  fall  short  of  expla- 
nation in  the  light  of  recognized  tests  projected  to  prevent 
such  failures.  There  then  arises  another  want  to  be  filled, 
a  gap  vacant  because  chemical  analyses,  physical  tests  and 
microscopical  examinations  do  not  enable  the  metallurgist 
to  throw  around  the  fruit  of  his  labors  the  fullest  possible 
precautions  intended  within  the  scope  of  such  tests.  Possi- 
bly fuller  information  is  to  be  found  by  supplementing 
already  established  tests  with  other  tests  to  approach  as 
near  as  possible  the  conditions  to  which  steel  castings  are 
subjected  in  service,  namely — vibratory  stresses.  A  study 
of  such  stresses  will  no  doubt  give  much  valuable  infor- 
mation and  change  certain  conditions  now  thought  to  be 
essential. 


CHAPTER  VII 


RELATldN   BETWEEN    COMPOSITION   AND   PHYSICAL    PROPER- 
TIES— CARBON — CAST  STEEL — TENSILE  STRENGTH — • 
DUCTILITY — ELASTICITY — ELASTIC  LIMIT — 
HARDNESS 

CARBON — In  order  to  understand  the  matter  under  con- 
sideration it  would  be  well  to  study  the  definition  of  steel. 
Principally  it  is  a  combination  of  iron  and  car- 
bon, and  certain  other  ingredients  to  be  regarded 
further,  without  any  sharply  defined  limits  as  to 
the  amount  of  carbon  alloy.  On  the  basis  of 
composition  alone  the  lower  amounts  may  equal 
those  found  in  wrought  iron,  and  going  to  the  other 
extreme  it  is  difficult  to  say  where  steel  ends  and  cast  iron 
or  pig  iron  begins.  The  composition  of  wrought  iron  in 
regard  to  carbon  may  range  from  traces  to  such  amounts 
as  0.07  per  cent,  yet  the  softer  steels  can  be 
produced  with  as  low  a  carbon  as  0.07  per  cent, 
but  the  physical  condition  may  be  quite  different  as 
compared  with  wrought  iron.  As  the  carbon  in- 
creases until  a  point  is  reached  at  or  about  2.5  per  cent 
the  combination  is  then  regarded  as  cast  iron,  the  latter 
being  the  crudest^form  from  which  by  various  processes  of 
purification  and  decarbonization  many  kinds  of  steel  are 
produced.  The  process  of  manufacturing  wrought  iron 
is  also  a  purifying  and  decarbonizing  one  with  an  essential 
difference  whereby,  in  a  sense,  the  former  is  a  product  of 


82  COMPOSITION   AND  PHYSICAL   PROPERTIES 


a  "dry"  method,  while  steel  with  any  range  of  carbon  is  the 
result  of  a  "wet"  one.  In  other  words,  the  temperature 
of  the  puddling  furnace  in  which  wrought  iron  is  made 
is  not  sufficiently  high  to  maintain  fusion  or  fluidity  com- 
pletely during  the  full  interval  of  the  progress  in  conver- 
sion and  purification.  The  initial  charge  is  composed 
mainly  of  pig  iron  with  a  total  carbon  of  between  2%  and 
4  per  cent,  which  readily  melts  and  because  of  certain 
active  influences  gradually  loses  its  carbon  but  gains  in 
plasticity  because  of  temperature  limitations  and  the  type 
of  furnace  used,  so  that  at  the  end  of  the  operation  there 
will  be  a  mass  of  almost  carbonless  iron  which  can  be  di- 
vided into  several  bulky,  spongy  balls  and  worked  into 
shapes.  On  the  other  hand,  steel  making  is  the  result  of  a 
process  conducted  under  temperature  conditions  wherein 
fusion  or  liquation  is  maintained  from  the  time  of  melting 
cold  stock  until  such  time  when  decarbonization  has  pro- 
ceeded to  almost  any  desired  extent,  so  that  with  a  proper 
type  of  furnace  and  necessary  thermal  ranges  it  is  possible 
to  equal  in  composition  the  commoner  analyses  of  wrought 
iron.  Thus,  it  will  be  understood  that  the  content  of  car-, 
bon  in  the  lower  ranges  will  not  suffice  to  mark  the 
division  between  iron  and  steel.  Another  difference  pres- 
ents itself  in,  perhaps,  a  mechanical  way.  That  is,  wrought 
iron  may  contain  slag  or  cinder  enveloping  its  fibres  vary- 
ing in  quality  between  0.2  per  cent  and  2.0  per 
cent,  and  which  will  play  an  important  part  upon 
its  physical  properties.  The  presence  of  cinder 
is  due  to  the  sponge-like  formation  of  plastic 
wrought  iron  in  its  last  stage  of  manufacture  en- 
closing slag  or  cinder.  Steel  being  produced  by  liquation 
permitting  a  separation  of  the  slag  and  liquid  metal  by 
gravity,  the  finished  product  will  be  practically  free  from 
mechanically  contained  cinder,  thus  securing  a  greater 
continuity  or  intimacy  within  itself  and  therefore  more 
strength  than  wrought  iron  containing  an  equal  amount  of 
carbon. 


COMPOSITION   AND   PHYSICAL  PROPERTIES  83 

The  metallurgy  of  steel  is  based  principally  upon  the 
influence  of  carbon  which  controls  the  familiar  properties 
of  strength,  ductility,  malleability,  weldability  and  most  of 
^all,  the  property  of  being  hardened  and  tempered.  The 
presence  of  carbon  in  iron  is  purely  accidental,  due  to  the 
use  of  carbonaceous  fuel  as  a  source  of  heat  in  smelting 
iron  ores.  Had  the  primitive  iron  makers  stumbled  upon 
some  other  substance  that  had  a  similar  power  of  separat- 
ing iron  from  its  earthy  matters,  we  might  today  be 
working  with  steel,  the  most  important  and  useful  of  all 
metals,  founded  upon  another  basal  element.  Nature,  in 
her  bounteousness,  has  given  us  coal  in  abundance.  It 
seems  the  simplest  fundamental  fuel  for  smelting  iron 
ores;  but  owing  to  the  affinity  that  exists  between  carbon 
and  iron  for  each  other  there  results  a  product  highly  car- 
bonized, yielding  a  metal  limited  in  its  capacity  for 
strength  and  ductility. 

Carbon  is  recognized  as  existing  in  iron  or  steel  in  sev- 
eral forms  with  a  variety  of  subdivisions ;  generally  it  is 
regarded  as  two  constitutional  divisions,  one  as  combined 
carbon  and  another  as  free  or  graphitic  carbon,  the  former 
being  a  definite  chemical  compound  of  iron  and  carbon, 
expressed  by  the  symbol  FesC,  and  the  latter  (graphite) 
nearly  pure  carbon.  It  is  stated  by  authorities  that  iron 
can  carry  theoretically,  about  two  per  cent  of  combined 
carbon  and  still  be  regarded  as  high  carbon  steel.  Should 
the  carbon  be  carried  beyond  that  point  and  if  heated  and 
cooled  slowly  the  pure  or  free  form  of  carbon  would  appear 
in  a  small  degree  and  the  alloy  would  then  be  on  the  bor- 
derland of  cast  iron.  As  is  well  known,  wrought  iron  and 
the  very  softest  steels  are  both  malleable,  ductile  and  weld- 
able,  but  as  the  content  of  carbon  increases,  those  proper- 
ties gradually  diminish  and  the  skill  to  work  them  be- 
comes of  a  higher  order  than  that  required  in  the  softer  or 
milder  grades.  Cast  iron  is  practically  unforgable  or 
weldable  merely  because  of  the  excess  of  carbon  present 
either  in  the  combined  or  free  state.  Summarizing  the 


84  COMPOSITION  AND  PHYSICAL  PROPERTIES 


general  explanations,  steel  may  be  regarded  as  a  matrix 
of  iron  in  which  is  dissolved  or  alloyed  varying  amounts 
of  combined  carbon,  with  an  absence  of  it  in  the  free  or 
graphitic  form;  a  freedom  from  slag  or  cinder,  the  prod- 
uct of  a  process  of  liquation  or  complete  fusion  through- 
out the  operation  of  refining  and  conversion. 

CAST  STEEL  is-  a  substance  distinguished  from  wrought 
iron,  in  that  during  certain  stages  of  manufacture  it  is  suf- 
ficiently liquid  to  pour  into  such  receptacles  as  metal  or 
sand  molds.  The  composition  of  the  product  may  cover 
wide  ranges.  Wrought  iron  as  already  stated  is  worked 
up  from  plastic  masses  of  partially  or  completely  decar- 
bonized cast  iron.  Open-hearth  castings  are  the  product 
of  liquid  steel  with  limited  composition  poured  into  molds 
composed  chiefly  of  silica  sand.  The  physical  properties 
must  conform  to  certain  requirements  of  strength,  tough- 
ness, ductility  and  soundness.  The  attainment  of  such  ob- 
jects is  brought  about  by  adjustments  of  chemical  compo- 
sitions during  the  process  of  refining  the  raw  material 
and  also  by  certain  methods  of  heat  treatment  applied  to 
the  finished  product.  Steel  castings  are  divided  into  three 
grades:  "soft,"  "medium;"  and  "hard."  Standard  speci- 
fications do  not  define  the  chemtcal  composition  of  each 
grade  but  give  attention  mainly  to  the  physical  properties 
as  cited  in  the  preceding  pages.  Generally  stated  the  fol- 
lowing figures  will  cover  the  composition  of  each  class  of 
castings : 

Carbon.  Silicon.  Sulphur.     Phosphorus.  Manganese. 

Soft       0.17-0.20  0.25-0.35  0.015-0.050        0.020-0.04        0.50-0.75 

Mediumo.2O-o.3O  0.25-0.35  0.015-0.050        0.020-0.04        0.50-0.75 

Hard      0.30-0.40            2  0.015-0.050        0.020-0.04        0.75-1.00 

TENSILE  STRENGTH  is  understood  as  the  resistance  of  a 
body  to  a  stretching  force  steadily  applied.  The  force 
necessary  to' produce  a  rupture  is  expressed  in  pounds  per 
square  inch  of  section. 


£    UNIVERSITY  ) 

V  n       °F  / 

^^UFOR\^X 
COMPOSITION  AND  PHYSICAL  PROPERTIES  85 


DUCTILITY  is  that  property  which  yields  to  a  tensile 
stres,s  and  produces  a  permanent  deformation  or  elonga- 
tion with  or  without  rupture.  It  is  expressed  in  "percent- 
age of  elongation"  and  is  measured  between  two  pre-deter- 
mined  points.  It  may  also  be  indicated  by  the  contraction 
of  area  when  a  specimen  is  measured,  before  and  after  the 
feature,  in  cross  section.  Not  only  will  a  specimen  in- 
crease in  length  under  a  certain  stress  but  at  one  point  it 
will  decrease  in  area  so  that  upon  fracture  there  may  be  a 
distinct  "necking"  and  the  rate  of  decrease  in  sectional 
area  is  expressed  in  "percentage  of  contraction,"  which, 
together  with  the  measured  elongation,  can  be  regarded  as 
indicies  of  ductility. 

ELASTICITY  is  that  point  where  a  permanent  deformation 
under  a  load  begins  or  where  a  specimen  fails  to  assume 
its  original  length  or  sectional  area  when  the  load  is  re- 
leased. This  definition  can  also  be  applied  to  describe  the 
arrival  of  a  "permanent  set."  The  determination  of  elastic 
limit  is  a  delicate  one  and  in  engineering  problems  is  very 
important,  representing  the  practical  value  of  a  casting. 
In  making  calculations  for  service  loads  the  elastic  limit  of 
the  metal  entering  into  castings  is  taken  as  a  basis,  not  the 
tensile  strength.  For  general  purposes  50  per  cent  of  the 
ultimate  or  tensile  strength  is  taken  as  the  value  of  the 
elastic  limit.  An  increasing  ratio  between  elastic  limit  and 
tensile  strength  is  a  prime  object  to  reach  in  high  grade 
products. 

HARDNESS  is  understood  as  the  property  of  a  body  to 
resist  the  static  penetration  of  another  harder  body,  or  it 
may  mean  the  ability  to  resist  attrition  caused  by  the 
movement  of  another  harder  body. 

Unfortunately  there  are  not  known  any  precise  data  as 
to  the  influence  of  carbon  in  steel  castings  upon  the  tensile 
strength  and  ductility  of  the  metal  in  them.  The  influence 
can  only  be  stated  in  general  terms  in  the  light  of  practice. 
To  get  exact  values  would  entail  difficult  researches;  it 
would  be  necessary  to  have  conditions  fixed  in  order  to 


86  COMPOSITION  AND  PHYSICLA   PROPERTIES 


study  the  influence  of  successive  increments  of  the  ele- 
ment. The  furnace  practice,  casting  temperatures  and 
heat  treatment  would  have  to  be  constant  in  each  case  for 
strict  comparisons.  The  contents  of  silicon,  sulphur,  phos- 
phorus and  manganese  would  have  to  be  subject  to  definite 
control  with  only  variations  permissible  in  the  carbon  of 
each  specimen  before  reliable  information  could  be  de- 
ducted. Experience  has  proven  as  a  recognized  fact  that 
carbon  is  both  a  hardening  and  strength  giving  agent. 
Reference  to  the  physical  requirements  of  the  three  grades 
of  castings  and  their  corresponding  chemical  analyses  will 
bear  out  the  general  assertion,  but  owing  to  other  disturb- 
ing influences,  more  or  less  potent,  the  ranges  of  analyses 
are  not  concordant  with  the  tensile  strength  and  ductility 
for  each  class.  That  is,  it  is  indefinite  that  a  0.17  to  0.20 
carbon  may  show  about  60,000  pounds  per  square  inch, 
and  a  given  elongation  and  contraction.  As  the  carbon 
increases  there  are  gains  in  strength  but  decreases  in  duc- 
tility in  the  remaining  grades.  Campbell  in  his  admirable 
work  on  the  "Manufacture  and  Properties  of  Structural 
Steel,"  gives  formulas  for  the  calculation  of  the  physical 
properties  on  the  basis  of  chemical  composition  and  in  a 
later  treatise1  revises  them,  giving  values  for  several  ele- 
ments common  to  steel,  making  a  distinction  between  acid 
and  basic  practice.  His  figures  apply  to  rolled  material  pro- 
duced under  fairly  regular  conditions,  but  it  would  seem 
inconsistent  to  apply  the  same  formulas  to  steel  castings 
manufactured  under  totally  dissimilar  methods.  Kent3 
quotes  Webster  giving  values  of  carbon  in  rolled  stock  in 
conjunction  with  three  other  elements,  sulphur,  phosphorus 
and  manganese,  as  a  constant  of  800  pounds  per  square 
inch  with  each  o.oi  per  cent  of  that  element  with  a  base 
value  of  34,75°  pounds  per  square  inch  for  carbonless 

journal  British  Iron  and  Steel  Institute,  No.  2,  1904,  pp.  21  to  62. 
"Mechanical  Engineers'  Pocketbook.  1904,  p.  389. 
3Iron  and  Steel  and  Other  Alloys,  1903,  pp.  192  to  162. 
Manufacture  and  Properties  of  Structural  Steel,  1896,  p.  329. 


COMPOSITION   AND   PHYSICAL   PROPERTIES  87 


wrought  irpn.  Prof.  H.  M.  Howe3  shows  that  the  harden- 
ing power  increases  with  the  carbon  content  and  also 
roughly  plots  a  curve  giving  a  direct  increase  in  strength 
varying  with  the  carbon  until  a  point  is  reached  near  1.20 
per  cent  when  the  strength  or  tenacity  rapidly  decreases, 
with  a  further  gain  in  carbon  up  to  three  per  cent,  where 
the  strength  then  remains  fairly  constant  up  to  4.50  per 
cent  of  that  element.  The  maximum  strength  at  1.20  per 
cent  being  about  140,000  pounds  per  square  inch  falling 
to  about  25,000  pounds  at  three  per  cent  and  at  4.50  per 
cent  to  about  18,000  pounds.  Campbell4  assumes  a  base 
value  of  wrought  iron  as  38,000  to  39,000  pounds  per 
square  inch  and  constructs  formulas  for  both  acid  and  basic 
steel  compositions  with  o.oi  per  cent  carbon  giving  1,210 
pounds  per  square  inch  for  each  point  gained  in  the  first 
named  grade  and  950  pounds  per  square  inch  for  each 
point  of  carbon  in  the  latter  grade,  but  which,  as  already 
stated,  apply  only  to  rolled  material.  In  steel  castings  the 
distributing  factors  are  so  numerous  that  it  seems  impos- 
sible to  formulate  precise  mathematical  computations  cov- 
ering the  physical  properties,  while  taking  into  account 
the  composition  and  values  of  each  element.  The  furnace 
practice,  perhaps,  the  greatest  factor  entering  into  the 
equation  and  since  no  two  heats  are  handled  exactly  alike 
in  all  particulars  the  problem  becomes  more  and  more  ab- 
struse. Character  of  stock,  flame  action,  oreing,  casting 
temperature,  recarbonizing  and  the  methods  of  doing  the 
same,  rate  of  cooling  in  the  sand,  either  in  dry  or  green 
sand  molds,  all  need  consideration  as  do  methods  of  heat 
treatment,  leading  one  into  a  maze  of  speculation.  Gen- 
eral terms,  therefore,  cannot  be  avoided.  Certain  authori- 
ties have  been  cited,  and  the  reader  is  at  liberty  to  form  his 
own  conclusions  as  to  which  can  or  may  be  followed  in 
attempting  to  give  a  value  to  carbon  and  its  influence  upon 
open-hearth  steel  castings. 

LICON. — To  the  gray  iron  founder  silicon  conveys  a 
ifferent  impression  than  to  the  steel  founder.    In  one  case 


88  COMPOSITION   AND   PHYSICAL   PROPERTIES 


it  is  regarded  as  a  softening  agent  because  of  its  property 
in  releasing  graphitic  carbon  in  the  cooling  of  gray  iron 
when  liquid  and  thus  lowering  the  combined  carbon  which 
tends  to  make  iron  castings  hard.  In  the  other  case,  the 
carbon  being  low  and  entirely  in  the  combined  state  with 
no  graphitic  carbon  liberated,  the  function  of  silicon  be- 
comes a  different  one.  To  a  slight  extent,  about  one-tenth 
that  of  carbon,  the  effect  is  to  harden  steel  castings.  Pri- 
marily the  purpose  of  adding  silicon  to  open-hearth  steel 
is  to  promote  solidity,  but  an  anomalous  condition  some- 
times arises  in  unsoundness  coupled  with  an  amount  of 
silicon  in  the  finished  product  usually  considered  enough 
to  produce  the  opposite  and  desired  effect — soundness.  In 
general  practice  0.30  per  cent  is  enough  to  give  freedom 
from  blow  holes,  but  if  unsoundness  still  presents  itself  an- 
other condition  is  operating  which  will  be  explained  later. 
To  greatly  exceed  that  figure  is  wasteful  and  would  tend 
to  induce  brittleness  in  the  castings  which,  however,  may 
be  more  or  less  modified  by  heat  treatment. 

Silicon  in  steel  casting  practice  is  depended  upon  mainly 
as  a  deoxidizer  and  the  action  may  be  understood  by  the 
following  equations: 

(1)  Solid  Solid  Solid  Gaseous 
FeO'+  C  =  Fe  +  CO 

As  already  explained  the  foregoing  reaction  always  oc- 
curs in  a  bath  of  molten  steel  until  some  agent  is  introduced 
that  possesses  a  greater  affinity  for  the  oxygen  combined 
with  iron  as  ferrous-oxMe.\  Silicon  being  available  for  the 
purpose  reacts  as  follows: 

(2)  Solid    Solid    Solid    Solid 
2FeO  +  Si  =  2Fe  +  SiO 

and  under  normal  conditions  stops  the  gaseous  formation 
assisting  the  production  of  sound  castings.  The  SiO» 
(silica)  being  lighter  than  iron  floats  upwards  to  the  sur- 
face and  becomes  part  of  the  slag. 


COMPOSITION  AND  PHYSICAL  PROPERTIES  89 

If  a  test-spoon  of  liquid  steel  be  taken  from  the  bath 
when  the  action  is  most  lively,  the  metal,  as  soon  as  it  be- 
gins to  solidify,  will  emit  volumes  of  minute  sparks  giving 
evidence  of  some  gas-forming  action  or  release  of  some 
gases  in  conformity  with  equation   (i).     If  the  specimen 
when  cold  is  separated  by  fracture,  a  sponge-like  texture 
will  be  noticed  as  the  result  of  the  afore-mentioned  escap- 
ing gases ;  and  which  will  suggest  what  might  be  expected 
were  such  metal  poured  into  castings  without  a  deoxidiz- 
ing or  solidifying  treatment.     Just  what  the  composition 
of  the  gases  are  is  not  clearly  known,  but  it  is  certain  that 
the  reaction  in  equation  (i)  is  largely  responsible  for  the 
greater  quantity  of  them.     Some  authorities  anticipate  the 
presence  of  such  gases  as  hydrogen  and  nitrogen.     Their 
presence  may  be  possible   in  pneumatic     processes,     but 
scarcely  in  open-hearth  steel  wherein  fluidity  of  the  bath 
is  maintained  by  the  heat  of  a  flame  action  radiated  through 
a  protective  layer  of  slag  and  entirely  away  from  the  pos- 
sible contamination  of  such  gases  subject  to  introduction 
with  the  atmospheric  air  necessary  for  flame  combustion 
and  which  do  not  come  in  direct  contact  with  the  metal 
below  the  slag.     Proof  is  ample  that  perfectly  sound  cast- 
ings can  be  made,  depending     solely     upon     deoxidizers 
which  possess  no  attraction  for  hydrogen     or     nitrogen; 
therefore  if  they  should  be  present  they  are  not  sensibly  in- 
dicated by  porosity.     Silicon  is  accredited  with  the  addi- 
tional property  of  increasing  the  power  of  steel  to  dis- 
solve or  occlude  gases.     The  question  is  largely  conject- 
ural because  from  practical  observations  the  evidence  in 
support  of  such  a  theory  is  wanting.    It  is  difficult  to  con- 
ceive of  a  solution  of  a  gas  in  a  solid  without  some  inti- 
mation of  pores;  if  such  pores  do  exist  they  can  only  at 
best  be  minutely  microscopic.     The  writer,  in  his  experi- 
ence, has  not  observed  any  condition  attributable  to  the  oc- 
clusion of  either  free  hydrogen  or  nitrogen  in  open-hearth 
steel  castings. 

The  question  of  the  influence  of  silicon  beyond  solidity 


90  COMPOSITION   AND  PHYSICAL   PROPERTIES 


has  no  bearing  on  weldability  or  forgability,  such  proper- 
ties not  being  considered  in  steel  castings. 

SULPHUR. — Perhaps  there  is  no  element  which  is  so 
strongly  stigmatized  as  an  enemy  in  steel  casting  practice. 
No  one  as  yet  has  claimed  that  it  is  harmful  in  the  finished 
casting,  yet  specifications  usually  state  that  it  shall  not  ex- 
ceed 0.05  per  cent,  and  for  what  reason  is  yet  not  under- 
stood. The  manufacturer  may  be  more  concerned  in  see- 
ing the  sulphur  excessive  rather  than  the  customer.  Wheth- 
er a  casting  may  carry  0.05  per  cent  or  more  cannot  af- 
fect its  value  in  service.  Whatever  harm  may  follow  an 
excess  of  sulphur  ought  to  manifest  itself  before  the  cast- 
ing is  stripped  from  the  mold  and  thus  prevent  it  reaching 
the  customer.  Authorities  state  that  sulphur  tends  to  make 
metal  "red-short,"  a  condition  existing  in  iron  and  steel  ex- 
hibiting itself  by  the  metal  crumbling  or  cracking  when 
being  worked,  rolled,  forged  or  welded  at  temperatures 
suitable  for  such  operations.  The  effect-  is  not  always  due 
to  the  presence  of  sulphur,  which  may  be  masked  or  modi- 
fied by  other  constituents.  In  steel  castings  it  is  said  to 
produce  "red-shortness"  also  and  which  may  be  described 
as  property  of  the  metal  to  separate  or  crack  at  points 
where  the  contractive  force  is  greatest  during  a  period 
when  the  metal  is  passing  from  a  liquid  to  a  viscous  semi- 
plastic  state.  The  condition  may  or  may  not  occur  in  con- 
cordance with  the  amount  of  sulphur  present.  "Red- 
shortness"  may  appear  with  a  very  low  sulphur  content  or 
it  may  be  absent  when  the  sulphur  is  considered  high,  so 
that  it  is  not  possible  to  scan  a  chemical  analysis  and  recon- 
cile the  varying  degrees  of  "red-short"  effects  with  them. 
It  is  possible  to  have  castings  of  a  given  design  molded 
repeatedly  under  as  near  as  possible  like  conditions  yet 
have  some  "red-short"  and  others  absolutely  free  from  any 
such  flaw  with  identically  the  same  steel  in  composition  in 
each  case.  Similar  designs  may  be  cast  in  acid  and  basic 
steel  separately.  The  acid  casting  may  not  be  "red-short," 
but  the  basic  badly  so,  or  vice  versa,  yet  in  the  first  instance 


COMPOSITION   AND   PHYSICAL  PROPERTIES 


the  sulphur  will  be  nearly  0.05  per  cent  and  in  the  other 
0.25  per  cent  or  less.  The  repetition  of  such  evidences  all 
tend  to  discredit  the  belief  that  sulphur  is  the  main  cause 
of  castings  being  "red-short"  in  the  mold.  The  presence 
of  manganese  exerts  an  effect  to  neutralize  sulphur's  "red- 
shortness"  without  changing  the  ultimate  analysis  of  sul- 
phur. An  excess  of  the  last  named  element  beyond  0.07 
per  cent  in  steel  castings  may  give  some  trouble,  but  gen- 
erally the  ranges  are  between  0.015  to  0.05  per  cent,  and 
within  them  it  is  practically  inert.  The  common  practice 
is  to  carry  the  manganese  at  or  about  0.75  per  cent  and 
with  that  quantity  the  usual  content  of  sulphur  will  exist 
entirely  as  a  harmless  sulphide  of  manganese.  Were  the 
manganese  much  lower  the  sulphur  then  might  exist  as  an 
iron  sulphide,  the  latter  combination  being  more  active  as 
a  "red-shortner"  than  the  former.  If  "red-shortness"  per- 
sistently appears  in  steel  castings  with  normal  analyses  an- 
other condition  is  active,  a  remedy  for  which  is  beyond 
any  effort  to  change  the  composition  to  control  it.  The 
conditions  under  which  the  metal  is  treated  in  the  melting 
and  the  design  of  the  pattern  or  details  of  molding  often 
play  a  more  important  role  in  producing  "red-short"  cast- 
ings than  sulphur/ 

PHOSPHORUS<^-This  element,  like  carbon,  is  a  hardening 
agent,  but  unlike  it,  its  hardening  influence  is  not  subject 
to  any  great  modification  by  heat  treatment.  An  excess  of 
the  element  produces  the  effect  of  "cold-shortness,"  the 
opposite  of  "red-shortness,"  a  property  of  weakness  under 
shock  or  impact;  a  condition  of  brittleness.  s  Where  cast- 
ings are  subjected  to  severe  strains  the  phosphorus  should 
be  kept  below  0.05  per  cent,  particularly  with  the  higher 
ranges  of  carbon.  Ordinary  castings  with  no  special  re- 
quirements can  carry  as  high  as  0.08  per  cent.  Phosphorus 
can  replace  carbon  as  a  hardener  and  when  the  carbon  is 

American  Standard  Specifications  For  Steel  Castings. 


92  COMPOSITION  AND  PHYSICAL  PROPERTIES 


Hard  Medium  Soft 

Tensile  strength,  pounds  per  square  inch      85,000  70,000  60,000 

Yield  point,  pounds  per  square  inch 38,250  31,500  27,000 

Elongation,  per  cent  in  two  inches 15  18  22 

Construction,  per  cent    20  25  30 

high  the  phosphorus  should  be  kept  low  because  an  excess 
of  two  or  more  hardeners  will  produce  disagreeable  brittle- 
ness,  so  to  preserve  toughness  it  is  a  good  practice  to  keep 
all  hardeners  as  low  as  possible,  depending  upon  one  ele- 
ment only  for  the  necessary  strengthening  effect.  The 
value  of  phosphorus  as  a  strengthening  agent  is  about  900 
pounds  per  square  inch  for  each  o.oi  per  cent. 

No  effect  is  known  traceable  to  phosphorus  upon  the 
condition  of  "red-shortness." 

MANGANESE. — This  element  is  one  of  the  most  useful 
in  steel  casting  practice  and  in  all  steel  making.  It  works 
in  conjunction  with  silicon  as  a  deoxidizer  and  assists  in 
the  removal  of  gases  in  a  very  similar  action  by  forming 
a  fusible  slag  with  the  oxygen  combined  with  the  ferrous- 
oxide^  When  found  in  castings  it  is  the  result,  usually,  of 
an  addition  of  ferro-manganese  used  at  the  end  of  the  re- 
fining operation  and  with  it  will  be  carried  in  a  certain 
amount  of  carbon.  Roughly  stated  five-eightieths  of  the 
manganese  in  excess  of  the  residual  amount  of  that  ele- 
ment in  the  bath  at  the  finishing  period  represents  the 
quantity  of  carbon  furnished  by  the  ferro-manganese  addi- 
tion. So  that  as  the  manganese  increases  there  will  also 
be  a  gain  in  strength  until  a  point  is  reached  at  or  about 
1.50  per  cent  when  a  disagreeable  weakness  and  brittleness 
result.  ;  If  the  manganese  is  kept  about  0.75  per  cent, 
other  elements  being  low,  brittleness  is  absent,  but  if  it  be 
carried  above  that  to  about  i  per  cent  it  is  necessary  to 
carefully  anneal  the  castings  because  without  that  they  will 
be  more  or  less  brittle.  Heat  treatment,  however,  improves 
them,  conferring  toughness,  elasticity,  ductility,  and 
strength,  provided  other  conditions  are  normal.  In  the 
higher  ranges  manganese  has  a  peculiar  and  contradictory 


COMPOSITION  AND  PHYSICAL  PROPERTIES  93 


action.  When  a  content  is  reached  at  or  about  1.50  per 
cent  the  metal  is  hard  and  brittle,  that  condition  remaining 
until  about  7  per  cent  is  reached;  the  metal  then  becomes 
both  tough  and  hard.  Between  7  and  14  per  cent  a  peculiar 
alloy  is  obtained,  known  as  Hadfield  steel,  which  possesses 
the  striking  property  of  unusual  toughness  and  hardness 
combined.  If  manganese  is  kept  between  0.70  to  0.75  per 
cent  in  finished  castings  good  results  ought  to  follow.  An 
excess  complicates  conditions,  while  falling  below  might 
cause  blow-holes,  "red-shortness,"  and  other  weakness  in 
products. 


CHAPTER  VIII 


BLOW  HOLES  IN  STEEL  CASTINGS — DISCUSSION  OF  CAUSES 


A  common  source  of  annoyance  in  steel  castings  is 
found  in  porosity  or  in  unsoundness.  The  ingot  manufac- 
turer finds  it  comparatively  easy  to  get  around  such  draw- 
backs by  liberal  discards  or  end  cropping  of  ingots  usually 
more  or  less  spongy  or  blow-holed  at  the  upper  end.  Not 
so  with  the  production  of  castings.  The  problem  of  pour- 
ing liquid  steel  into  the  green  or  dry  sand  molds  has  a 
distinctive  complexity  in  comparison  with  casting  into  in- 
got molds  made  of  iron  or  dry  sand  with  simple  lines  or 
shapes. 

Blow  holes  in  a  steel  casting  may  be  due  to  a  variety  of 
causes.  They  must  not  be  confounded  with  "shrink 
holes"  or  cavities  due  to  a  difference  in  the  rate  of  cooling 
of  parts  contrasting  in  dimensions.  A  light  section  in  con- 
junction with  a  heavier  one  will  cool  faster  and  in  doing 
so  will  draw  upon  the  heavier  and  more  liquid  section,  thus 
depleting  it  of  steel,  with  the  result  that  in  the  heavier  sec- 
tion there  will  be  some  voids.  Hence  the  important  reason 
for  forming  larger  headers  or  reservoirs  to  hold  a  supply 
of  steel  from  which  the  casting  below  can  make  drafts  to 
offset  the  contraction  in  cooling.  Frequently  in  separating 
such  headers  rough  irregular  cavities  will  be  found  at  the 
joint  of  the  header  and  the  castings  which  are  known  as 
"shrink  holes,"  (see  Fig.  11)  and  may  be  formed  even  in 
cases  of  the  casting  being  free  from  "blow  holes."  The 


CAUSES  OF  BLOW  HOLES 


95 


position  of  cavities  or  pores,  due  to  either  gases  or  shrink- 
age, will  determine  their  identification. 

Blow  holes  may  be  found  in  any  part  of  a  machined  or 
fractured  casting.  Shrink  holes  occur  only  at  certain 
points.  They  are  irregular  in  shape,  with  rough  surfaces, 
but  upon  close  examination  will  be  found  covered,  with 
delicate,  minute  crystals.  The  walls  of  a  shrink  hole  are 
usually  the  same  color  as  the  metal  itself,  provided  no  air 
was  present  while  the  casting  was  hot.  Blow  holes  are  al- 
ways the  result  of  air,  vapor  or  gas.  Their  shape  as  a  rule 
is  oblong,  lenticular  or  spherical.  If  oblong  in  shape  they 
are  due  to  metal  being  imperfectly  deoxidized  or  "killed" 


FIG.    11. — SHRINK    HOLE.     DOTTED    OUTLINE    SHOWS    POSITION    OF 

RISER 


and  they  will  always  be  found  with  their  axes  or  longest 
dimensions  at  right  angles  to  the  cooling  surface  of  the 
body  of  metal  (see  Fig.  12).  If  they  are  globular  or 
spherical  they  are  caused  by  vapor  or  air  and  not  by  gas 
or  gases,  the  result  of  chemical  action  within  the  metal, 
but  by  damp  sand,  imperfect  venting — details  of  molding. 
While  it  is  perfectly  possible  (and  is  regularly  done)  to 
get  sound,  solid  steel  machinery  castings  from  green  sand 


CAUSES  OF  BLOW  HOLES 


molds,  accidental  causes  may  make  the  sand  too  damp.  In 
that  case  there  may  be  blow  holes  because  of  an  excess  of 
steam  or  aqueous  vapor  formed  by  the  hot  steel. 


]P  art  in, 


00000000 


O  o 

O  o 

o  o 

00000  000 


lAne 


FIG.    12.— BLOW   HOLES   CAUSED  BY   GASEOUS    STEEL    IMPERFECTLY 

DEOXIDIZED. 

If  the  green  sand  mold  should  possess  the  right  "temper" 
and  globular,  spherical  holes  still  be  found,  there  may  be 
two  causes  effective.  One  may  be  that  the  sand,  green  or 
dry,  is  too  close  or  too  strong,  preventing  a  free  escape  of 
the  gases  as  they  are  formed  by  the  heat  of  the  inflowing 
steel  upon  such  binders  as  may  be  used  to  give  body  to  the 


Parting 


00  O  C 

o        o      o       < 
o  o         o 

o       o       o        o 


Line 


Drag 

FIG.    13.— BLOW    HOLES    CAUSED    BY    DAMP    SAND,   VAPORS    FROM 
CORE — RENDERS   IMPERFECT  VENTING 


sand  and  cores.  Evidence  of  that  may  be  seen  in  fractured 
castings,  which  will  have  a  solid  drag  side,  but  a  more  or 
less  porous  cope  side  (see  Fig.  13).  A  casting  blown  be- 


CAUSES  OF  BLOW  HOLES  97 


cause  of  gaseous  or  improperly  "killed"  metal  will  be  more 
or  less  spongy  at  all  points  of  both  drag  and  cope.  Poro- 
sity is  often  caused  by  failure  to  freely  vent  the  highest 
points  of  the  cope  which  will  cause  air  pockets  to  be 
formed  which  the  liquid  steel  may  not  be  able  to  displace 
and  such  conditions  as  described  can  occur  in  spite  of  dry 
and  good  green  sand  molding  or  properly  deoxidized  steel. 
Thus  it  will  be  understood  that  in  spite  of  the  highest  skill 
manifested  in  the  melting  department,  it  may  be  nullified 
by  conditions  on  the  molding  floor.  A  study  of  the  daily 
discard  in  the  scrap  pile  as  it  is  broken  up  will  be  a  good 
guide,  as  to  what  errors  are  being  made  in  practice,  and 
with  a  slight  knowledge  of  the  causes  of  porosity  one  can 
greatly  modify  faults. 

If  the  chemical  analyses  are  normal,  that  is,  the  figures 
on  manganese  and  silicon,  are  within  usual  limits,  but  blow 
holes  of  the  oblong  character  are  persistent,  the  cause  can 
be  traced  to  the  furnace  platform.  There  may  be  too  sharp 
a  melting  flame,  too  much  air  admitted  for  flame  combus- 
tion, or  a  too  liberal  use  of  ore  in  refining.  Any  one  of 
these  conditions  will  surcharge  the  metal  with  oxide  be- 
yond the  influence  of  the  usual  addition  of  the  deoxidizers, 
manganese  or  silicon.  Such  practice  may  be  covered  up 
or  lessened  by  an  increase  of  deoxidizers,  but  always  at 
the  sacrifice  of  the  physical  requisite  in  steel  castings, 
toughness.  The  writer  knows  from  his  experience  in  ad- 
vanced steel  casting  practice  in  either  green  or  dry  sand, 
acid  or  basic  steel,  that  it  is  possible  to  produce  sound  cast- 
ings free  from  pin  holes  or  blow  holes  which  will  satisfy 
the  most  exacting  demands.  Still  there  is  no  royal  way  to 
the  production  of  sound  castings.  It  is  fraught  with  pa- 
tience, skill,  study  and  industry. 


CHAPTER  IX 

DISCUSSION     OF    THE     CAUSES     OF     CRACKS     IN     STEEL 
CASTINGS 

One  of  the  most  common  sources  of  weakness  in  steel 
castings  is  the  liability  to  crack  in  the  mold.  The  condi- 
tion is  the  result  of  "red-shortness."  It  is  an  annoyance 
and  a  continual  point  of  contention  between  the  melter  and 
the  molder,  each  blaming  the  other  for  his  share  in  the 
cause,  the  molder  claiming  the  steel  as  it  leaves  the  furnace 
is  not  just  what  it  should  be  and  the  melter  saying  that  the 
metal  is  faultily  cast  in  the  desired  forms  without  any  con- 
sideration as  to  the  proper  distribution  of  metal  in  the  light 
and  heavy  sections  of  a  casting.  From  the  standpoint  of 
the  metallurgist  the  melter  is  at  times  to  blame  and  at  other 
times  the  molder,  or,  going  further,  the  engineer  who  sub- 
mits the  designs  to  be  cast. 

The  condition  of  ''red-shortness"  or  cracks  is  far  from 
obliging  and  may  present  itself  at  the  most  unexpected 
and  inopportune  times.  If  in  a  given  heat  of  steel  there 
should  be  found  a  number  of  discards  among  various  de- 
signs because  of  cracks  and  the  trouble  continues  for  a 
long  period,  it  is  safe  to  say  that  the  metal  is  not  receiv- 
ing the  proper  treatment  in  the  furnace.  If  cracks  appear 
only  in  one  design  in  a  given  heat  of  steel  among  other  and 
different  designs,  the  trouble  is  due  to  some  fault  either  in 
•a  molding  detail  or  the  lines  of  the  casting.  In  other  words 
a  few  discards  in  keeping  with  an  average  loss  of  bad 
castings  cannot  be  blamed  upon  the  metal. 


CAUSES   OF   CRACKS    IN    CASTINGS  99 


As  discussed  in  previous  sections,  if  "red-shortness"  is 
troublesome  attempts  are  frequently  made  to  reach  a  low- 
er sulphur  analysis,  but  not  with  success.  It  has  been 
thought  that  in  doing  so  the  trouble  might  abate,  because 
the  element  sulphur  is  given  the  credit  for  "red-short" 
effects  and  that  a  correction  could  only  be  found  in  the 
composition.  If  cracks  are  numerous  the  cause  is  mainly 
due  to  the  flame  character  in  melting  and  the  way  the  re- 
fining is  conducted.  Through  such  conditions  the  metal 
becomes  contaminated  with  an  oxide  of  iron  that  acts  in 
a  measure  precisely  the  same  as  sulphur  is  said  to  do,  and 
what  may  seem  strange,  also,  is  that  it  is  possible  to  deoxi- 
dize the  metal  to  the  extent  that  blow-holes  caused  by 
gaseous  steel  are  practically  absent,  yet  "red-shortness" 
will  still  be  causing  trouble.  Numerous  instances  have 
been  observed  in  practice  which  point  to  the  fact  that  there 
must  be  an  indefinable  form  of  oxide  (iron)  that  does  not 
submit  to  the  cleansing  action  of  silicon  and  manganese 
as  final  additions.  In  such  a  case  as  soon  as  the  furnace 
manipulation  could  be  brought  under  control  a  very  seri- 
ous campaign  of  cracked  castings  was  stopped  without  any 
change  in  design  of  castings,  methods  of  molding  or  analy- 
sis of  finished  product.  There  could  be  noticed  also  a 
change  in  the  fracture  of  the  metal  in  regard  to  the  ap- 
pearance of  the  crystals,  another  evidence  which  could  be 
traced  back  to  furnace  manipulation,  which  is  in  a  great 
measure  responsible  for  "red-shortness"  in  castings,  in- 
dependently of  the  amount  of  sulphur  initially  or  finally. 

In  regard  to  molding  conditions  and  their  influence  upon 
cracks  the  trouble  often  lies  in  several  directions.  Steel  in 
cooling  contracts  much  more  than  gray  iron  cast  from  a 
similar  temperature.  There  is  a  point  where  the  steel  has 
lost  its  fluidity  and  is  more  or  less  viscous,  but  is  without 
stability  and  will  crumble  under  pressure.  When  the  steel 
passes  to  a  lower  temperature  it  seems  to  increase  in  den- 
sity and  becomes  more  or  less  malleable.  At  the  viscous 
point  should  there  be  any  resistance  offered  to  the  metal 


100          CAUSES  OF  CRACKS  IN  CASTINGS 


while  cooling  and  contracting,  because  of  improper  dis- 
tribution of  metal  or  absence  of  fillets  at  angles,  or  of  a 
flask  bar,  hard  core,  core  arbor  or  hard  molding  sand,  there 
is  danger  of  a  separation  or  a  crack  (a  crumbling  of  the 
metal)  at  that  point  where  the  contractive  force  could  not 
overcome  the  resistance  of  the  obstacles  mentioned. 
Should  the  metal  be  "over-oxidized"  at  the  range  of  tem- 
perature where  viscosity  is  manifest,  the  liability  to  crum- 
ble is  aggravated  and  the  castings  will  crack  with  very 
slight  resistance  from  the  causes  mentioned. 

It  is  not  to  be  supposed  that  should  the  metal  be  abso- 
lutely free  from  oxide  it  will  not  crack  even  under  extreme 
resistance  of  mold  parts.  The  conditions  of  crumbling 
under  slight  pressure  at  a  high  heat,  near  the  melting  point, 
are  peculiar  to  all  carbon  steels.  Therefore,  if  the  steel 
were  ever  so  pure  it  would  crack  if  held  rigidly  while  cool- 
ing and  contracting. 

Let  the  metal  be  poorly  handled  in  the  furnace  and  many 
cracks  will  appear  in  spite  of  care  on  the  part  of  the  mold- 
er.  If,  however,  due  care  is  observed  in  the  position  of 
the  gate  to  allow  a  uniform  cooling  of  the  metal  in  the 
mold,  cores  are  made  of  such  a  mixture  that  under  the 
heat  of  the  liquid  metal  they  will  crumble  to  dust  or  non- 
resisting  masses,  ample  sand  space  between  flasks,  bars 
and  projections  on  castings  provided,  and  molding  sand 
used  of  such  a  texture  that  when  subjected  to  a  high  tem- 
perature it  will  become  non-resistant,  then,  with  good  met- 
al, cracked  castings  need  not  cause  much  worry  by  a  low 
yield  of  salable  product. 


CHAPTER  X 


HEAT  TREATMENT  AND  ANNEALING — CONSIDERATION   OF 
THE  RELATION  BETWEEN  STRUCTURE,  HEAT  TREAT- 
MENT AND  PHYSICAL  CONDITION 

Under  heading-  of  heat  treatment  and  annealing  it  is  not 
proposed  to  advance  arguments  as  to  whether  or  not  steel 
castings  should  be  annealed  since  some  opinions  are  held 
that  it  is  not  necessary  with  certain  compositions  chemical- 
ly. Rather  the  remarks  herein  will  be  an  explanation  of 
what  occurs  when  cast  steel  is  given  various  heat  treat- 
ments. 

From  a  theoretical  standpoint  all  steel  castings  should  be 
annealed.  Practically  it  is  difficult  to  properly  undertake 
the  operation,  particularly  when  the  tonnage  may  be  large, 
as  then  the  process  presents  commercial  considerations.  If 
specifications  are  rigid  it  is  important  to  carefully  anneal, 
and  it  is  at  this  point  that  the  nub  of  the  question  arises. 
To  keep  the  output  parallel  with  deliveries  would  involve 
an  extensive  array  of  annealing  furnaces,  and  since  most 
foundries  are  without  capacity  to  anneal  their  entire  output, 
an  attempt  to  treat  all  castings  produced  would  result  in 
a  slighting  of  the  necessary  care  to  get  the  best  out  of  the 
process.  It  is  better  not  to  anneal  at  all  than  carry  it  out 
without  each  casting  getting  a  proper  treatment  under 
skillful  conditions.  Annealing  is  a  waste  of  time  and 
money  without  this  proper  and  skillful  care  in  the  work. 

In  general  most  metallurgists   view  heat   treatment   as 


IO2  HEAT  TREATMENT  AND  ANNEALING. 


primarily  a  method  to  equalize  or  lessen  strains  and 
stresses  set  up  in  a  casting  during  cooling  in  the  mold,  es- 
pecially when  the  shape  may  be  complicated  by  intricate 
parts  or  light  and  heavy  sections  combined.  True  a  re- 
heating will  tend  to  adjust  these  strains  but  really  heat- 
treatment  is  a  method  to  procure  in  a  casting  the  best  pos- 
sible conditions  in  the  internal  structure  consistent  with  the 
physical  properties. 

To  understand  what  is  involved  in  the  more  advanced 
practice  necessitates  a  consideration  of  the  relation  between 
structure,  heat-treatment  and  physical  conditions. 

The  internal  structure  or  crystalline  formation  depends 
mainly  upon  the  casting  temperature  and  the  rate  of  cool- 
ing from  that  temperature.  It  is  known  that  the  physical 
properties  reflect  in  a  large  degree  the  size,  shape  and 
character  of  the  crystals  formed  in  steel  castings.  If  a 
freshly  fractured  surface  of  a  steel  casting  cooled  normal- 
ly from  casting  temperature  be  examined,  to  the  eye  the 
grain  will  be  coarse  and  large.  If  the  same  casting  be  re- 
heated to  a  much  lower  temperature  than  that  at  which  it 
was  cast,  say  a  bright  red,  cooled  and  again  fractured  it 
will  be  noticed  that  grains  or  crystals  are  much  smaller 
and  closer  than  in  the  original  piece.  It  will  also  be  no- 
ticed that  after  the  re-heating  it  was  more  difficult  to  pro- 
duce fracture  than  in  the  first  instance,  that  the  metal 
seemed  tougher.  These  facts  give  but  a  hint  of  the  potent 
changes  set  up. 

The  refinement  of  the  crystals  when  subjected  to  varying 
ranges  of  temperature  and  rates  of  cooling  offer  interesting 
features  which  to  fully  appreciate,  requires  a  delving  into 
their  details  by  means  of  a  microscope.  The  microscopic 
examination  of  metals  has  developed  a  comparatively  new 
science  known  as  "Metallography"  and  with  it  a  number 
of  terms  which  apply  to  crystalline  formations  in  metals 
not  visible  to  the  unaided  eye. 

Before  going  into  a  recounting  of  the  constituents  visible 
through  the  microscope  and  formed  in  cast  steel,  the 


HEAT  TREATMENT  AND  ANNEALING 


I03 


changes  produced  by  heat  treatment  upon  the  physical 
properties  will  be  considered. 

If  a  piece  of  cast  steel  be  allowed  to  cool  freely  from  a 
casting  temperature  there  will  be  a  grain  or  crystal  growth 
proceeding  to  a  certain  point  when  the  growth  ceases.  The 
metal  in  that  condition  will  not  possess  its  maximum  duc- 
tility expressed  as  elongation  and  contraction  of  area.  It 
will  be  more  or  less  brittle,  depending  upon  the  carbon 
content.  If  that  same  piece  of  steel  be  re-heated  to  or 
about  the  point  at  which  the  grain  growth  stopped  and  al- 
lowed to  cool  slowly,  the  coarse  grain  developed  during 
the  first  cooling  will  be  greatly  modified,  broken  up  or  ob- 
literated and  replaced  by  a  finer  grain  than  it  had  origi- 
nally. In  this  new  condition  the  ductility  will  be  greatly 
improved;  the  metal  will  be  tougher  and  better  fitted  for 
service  conditions  in  any  case  than  without  a  re-heating. 
Such  a  re-heating  is  properly  speaking  "annealing."  The 
object  then  in  annealing  is  to  so  affect  the  grains  or  crys- 
tals as  to  develop  the  maximum  degree  of  toughness  that 
a  casting  of  a  given  composition  is  capable  of  developing. 

By  referring  to  Fig.  14,  an  idea  will  be  suggested  as  to 


FIG.  14. — SHOWING  STRUCTURAL  CHANGES 


the  changes  taking  place  in  structure  by  heating.  The  ex- 
amination was  made  on  a  piece  of  0.25  carbon  steel  pos- 
sessing a  coarse  structure  common  to  steel  of  that  compo- 
sition cooled  normally  from  casting  temperature.  The  ar- 
rows indicate  the  temperature  to  which  the  specimens  were 


IO4  HEAT   TREATMENT   AND  ANNEALING 


heated  and  immediately  allowed  to  cool.  The  heat  was  ob- 
tained in  an  electrical  muffle  furnace  and  the  temperature 
measured  by  a  Le  Chatelier  pyrometer.  The  structures 
were  noted  microscopically.  The  range  "W"  refers  to  re- 
calescence  or  refining  temperature.  It  is  that  range  ther- 
mometrically  at  which  all  coarse  crystallization  acquired  in 
cooling  from  temperatures  above  "W"  and  near  the  melt- 
ing point  is  changed  and  replaced  with  a  finer  structure  or 
as  fine  as  it  is  possible  to  get  in  an  ordinary  piece  of  cast 
steel.  A  re-heating  below  "W"  does  not  accomplish  any- 
thing in  cast  steel.  A  re-heating  greatly  above  "W"  causes 
the  grain  to  again  grow  after  it  had  been  refined  while 
the  piece  was  passing  through  the  recalescence  period. 

To  grain-refine  a  piece  of  cast  steel  it  is  necessary  to 
pass  through  and  slightly  above  "W,"  and  after  that  point 
has  been  reached  nothing  is  to  be  gained  by  a  prolonged 
or  higher  heating.  That  is  to  say,  if  the  piece  is  heated 
throughout  at  the  needful  refining  temperature  the  fire 
may  be  drawn  or  if  the  shape  will  permit  it,  it  can  be  air- 
cooled  immediately.  In  doing  so  all  stresses  will  be  mini- 
mized and  no  matter  what  the  previous  structure  may  have 
been,  the  irregularities  of  original  stress  and  grain  will 
be  removed  by  heating  the  mass  to  a  uniform  color  (slight- 
ly above  "W")  and  then  allowing  it  to  cool  uniformly. 

The  equation  of  time  for  grain  refinement  depends  large- 
ly upon  the  size  and  shape  of  the  piece;  a  wire  may  be 
brought  to  the  right  heat  in  a  few  moments.  Then  it 
should  be  withdrawn  because  a  longer  heating  is  needless. 
A  cube  8  inches  or  more  in  section  might  take 
several  hours  to  refine  it  and  heat  it  through, 
but  as  soon  as  uniformly  heated  and  refined  there  is  abso- 
lutely nothing  to  be  gained  by  heating  further.  Longer 
heating  would  result  in  grain  enlargement,  a  decrease  in 
ductility,  toughness,  a  heavy  scaling  of  the  piece  and  a  su- 
perficial de-carbonization  as  in  malleableizing  if  "W"  is 
greatly  exceeded.  To  sum  up  the  question  of  temperature 
and  its  effect  upon  grain  size  Prof.  Sauveur  says: 


HEAT  TREATMENT   AND   ANNEALING 


105 


(1)  "When  a  piece  of  steel,  hardened  or  unhardened, 
is  heated  to  the  temperature  'W,'  all  previous  crystalliza- 
tion however  coarse  or  however  distorted  by  cold  working, 
is  obliterated  and  replaced  by  the  finest  structure  which 
the  metal  is  capable  of  assuming." 

(2)  "The    higher    the    temperature    above    'W    from 
which  the  steel  is  allowed  to  cool  undisturbedly  the  larger 
the  grains." 

(3)  "The  slower  the  cooling  from  a  temperature  above 
'W  the  larger  the  grains."   "The  Metallographist,"  Vol. 
2,  pp.  265  and  266. 

So  much  for  temperature  and  corresponding  grain 
growths.  The  matter  in  the  following  table  is  selected 
from  averages  obtained  in  researches  conducted  some  four 
years  ago  by  the  writer  upon  the  effect  of  grain  size  as  af- 
fecting the  physical  properties  of  cast-steel : 

Tensile 

strength,          Elonga-          Contrac- 
pounds,          tion  per         tion  per 
sq.  in.  cent.  cent.  Treatment. 

Series  I. 

80,385  13.26  16.2     Metal  as  cast. 

78,767  27.20  40.4     Heated  to  "W." 

79,422  14.80  15.3     Greatly  above  "W." 

Series  II. 

77,779  26.5  28.5     Metal  as  cast. 

74,504  25.0  48.8     Heated    to   830    degrees    Fahr., 

quenched,  reheated  to  750  and 

air  cooled. 
78,792  25.0  34.3     Heated    to    815    degrees    Fahr., 

one  hour  and  air  cooled. 
74,058  25.7  31.      Heated  24  hours  at  850  degrees 

Fahr.        Cooled       in      furnace. 

Four  hours  in  heating.   Eleven 

hours    cooling. 
73,376  24.2  26.7     Heated   36   hours    between   850 

to  900  degrees  Fahr.     Heating 

up    3    hours    15    min.      Cooling 

down  9:45. 
90,400  2.5  3.       Heated  to  1,200  degrees  Fahr., 

and  quenched. 


io6 


HEAT  TREATMENT  AND  ANNEALING 


In  the  foregoing  Series  I  are  the  averages  of  a  number 
of  bars  from  one  heat  of  steel  and  Series  II  from  another 
heat.  A  study  of  the  figures  will  readily  show  what  can 
be  done  in  arriving  at  different  physical  properties  by  vary- 
ing the  heat-treatment.  Reference  to  diagram  Fig.  15, 
which  is  a  record  of  some  extreme  tests  carried  out  by 
the  United  States  government  at  Watertown  arsenal,  will 


020,000 


1        2 


FIG.   15.— RECORD  OF  GOVERNMENT  TESTS 

still  further  enlighten  one  as  to  the  contrasting  behavior 
physically  affected  by  heat  treatment.  These  experiments 
in  conjunction  with  others  on  record  show,  that,  unless 
the  heat-treatment  is  a  constant  and  other  conditions  nor- 
mal in  steel  casting  practice,  it  is  not  possible  to  readily 
forecast,  by  means  of  formulas,  the  physical  properties  tak- 
ing into  account  the  chemical  composition. 

The  ranges  of  ductility  and  tensile  strength  seemingly 
vary  with  temperature  and  rate  of  cooling.    The  treatment 


HEAT   TREATMENT  AND  ANNEALING  IO7 


that  will  give  the  maximum  degree  of  elasticity  combined 
with  the  maximum  degree  of  ductility  is  the  one  that  should 
be  aimed  at  in  high  grade  product. 

The  strength  or  elasticity  depends  upon  the  amount  of 
carbon  present  and  the  form  that  it  assumes  as  a  result  of 
the  heat  treatment  it  may  receive. 

Ductility  depends  upon  the  smallest  possible  degree  of 
refinement  or  non-crystalline  formation  structurally  that 
the  carbon-iron  alloy  is  capable  of  assuming.  These  re- 
finements control  the  annealing  or  heat-treatment  methods 
and  satisfactory  results  cannot  be  obtained  in  practice  with- 
out an  observance  of  the  laws  governing  them.  The  pro- 
cess can  best  be  studied  with  the  aid  of  a  microscope.  Pho- 
tomicrograph Fig.  1 6  is  a  view  showing  the  structure  of 
0.25  carbon  cast  steel  magnified  190  times.  Fig.  17  shows 
the  same  steel  heated  to  1,200  degrees  Fahr.  and  cooled 
slowly  in  the  furnace.  Fig.  18  is  the  same  steel  heated  to 
1,200  degrees  Fahr.  and  air  cooled.  In  Fig.  19  it  was 
heated  to  825  degrees  Fahr.  and  air  cooled.  All  photomi- 
crographs are  magnified  the  same,  and  a  study  of  the  vari- 
ous formations  in  conjunction  with  the  physical  properties 
as  tabulated  will  show  plainly  what  is  accomplished  in  cast 
steel  by  heating  and  cooling  differently.  Figs.  16,  17  and 
18  are  all  coarse  and  more  or  less  brittle.  Fig.  19  shows 
the  refinement  obtained  at  "W"  and  with  it  will  be  found 
physically  a  great  improvement  in  ductility.  In  each  case 
the  composition  is  precisely  the  same  since  each  specimen 
was  cut  from  one  bar  of  steel. 

Some  attention  will  now  be  given  to  the  constituents  rec- 
ognized microscopically  in  steel. 

First  in  order  comes  "Ferrite"  which  may  be  seen  in  the 
submitted  photomicrographs  by  the  white  areas.  It  is 
nearly  pure  iron,  that  is,  carbonless  (plus  Si,  S,  P,  and 
Mn,).  It  is  soft,  weak  and  ductile. 

Next  in  importance  is  "Cementite,"  and  which  is  not  free 
or  visible  separately  in  ordinary  cast  steel.  It  is  the  car- 
bon-iron alloy  and  is  expressed  definitely  as  FeaC.  It  is 


IO8  HEAT  TREATMENT  AND   ANNEALING 


that  constituent  which  confers  hardness,     elasticity     and 
strength  upon  steel. 

Finally,  there  is  "Pearlite,"  which  is  distinguished  from 
"Ferrite"  by  the  dark  areas  shown  in  the  photographs.  It 
is  a  mixture  or  combination  of  "Cementite"  and  "Ferrite" 
in  the  proportion  of  i  to  6.  The  constituents  as  named  are 
the  only  ones  that  enter  in  the  problems  of  annealing  cast 
steel.  (There  are  others,  such  as  martensite,  troosite,  etc., 
which  are  only  found  in  steels  that  may  be  hardened  and 
tempered.)  Cementite  is  not  structurally  free  until  the 
carbon  exceeds  0.9  per  cent.  Pearlite  is  recognized  as  ex- 
isting in  three  forms.  In  photomicrograph  Fig.  16  it  is 
called  "lamellar"  and  is  always  found  in  steel  slowly 
cooled  from  a  high  temperature  (in  this  case  from  a  cast- 
ing temperature  of  nearly  1,600  degrees  Fahr.).  Fig.  17 
indicates  also  cooling  but  from  a  lower  temperature.  The 
structure  is  still  "lamellar"  but  not  distinctly  so.  Fig.  18, 
cooled  at  a  quicker  rate  (air  quenching)  but  from  the  same 
temperature  as  Fig.  17  is  called  "sorbitic"  pearlite.  The 
physical  properties  accompanying  such  a  structure  would 
be  slightly  stiffer  than  in  Fig.  17  with  about  the  same  duc- 
tility. In  Fig.  1 6  the  ductility  is  low  but  with  a  higher 


FIG.  16.— SPECIMEN  OF  CAST       FIG.    17.— SAME    STEEL    HEATED    TO 
STEEL  IN  CONDITION  AS  1,200°    CENT.    (2,192°   FAHR.) 

CAST  (Am  COOLED)  AND  COOLED  SLOWLY  IN 

THE  FOUNDRY 


HEAT   TREATMENT   AND   ANNEALING 


tensile  strength  than  Figs.  17  and  18.  Fig.  19  gives  a  view 
of  "granular"  pearlite  and  is  one  sought  when  ductility 
and  resistance  to  shock  are  necessary.  The  tensile  strength 
with  such  a  structure  is  slightly  lower  than  those  of  the 
preceding.  In  the  last  structure  we  have  a  view  of  the 
marked  change  that  has  occurred  by  a  heating  to  "W"  when 
the  previous  structure  was  as  shown  in  Fig.  16  and  also 
in  the  other  photographs  what  occurs  in  grain  growth 
when  the  temperature  is  carried  far  above  "W."  Were 
the  temperature  increased  to  or  about  1,500  degrees  Fahr. 
there  would  have  been  in  Figs.  17,  18  and  19  about  the 
same  formation  as  in  Fig.  16. 


FIG.  18. — SAME  STEEL  HEATED  TO 
1,200°  CENT.  (1,192°  FAHR.)  AND 
AIR  QUENCHED 


FIG.  19. — SAME  STEEL  HEAT- 
ED TO  800°  CENT.  (1,472° 
FAHR.)  AND  COOLED  IN 
AIR.  AN  IDEAL  STRUCT- 
URE FOR  STEEL  CASTINGS 


A  study  of  Fig.  16  reveals  a  reason  why  cast  steel  unan- 
nealed  is  more  or  less  brittle  and  snaps  or  fails  suddenly 
on  shock  or  impact.  The  dark  areas  or  the  carbon  com- 
pound is  comparatively  hard,  while  the  light  or  carbonless 
areas  are  weak  and  there  is  an  uneven  distribution  of  the 
strong  and  weak  parts  so  that  the  ferrite  areas  offer  planes 
of  cleavage  under  stress. 


IIO  HEAT  TREATMENT  AND  ANNEALING 


When  the  structure  is  broken  up  as  in  Fig.  19,  the 
crystals  are  very  small  with  an  even  intermingling  of  the 
several  constituents  with  cleavage  planes  practically  re- 
duced to  nil.  A  fracture  occuring  in  cast-steel  with  a 
coarse  structure  always  follows  the  ferrite  areas  and  it  is 
not  known  that  the  line  of  separation  passes  through  the 
pearlite.  A  coarse  microstructure  usually  accompanies  a 
coarse  fracture  while  a  fine  microstructure  will  show  a  fine, 
silky  fracture. 


CHAPTER  XI 


REPAIR  OF  STEEL  CASTINGS  WITH  THERMIT  —  " 
ON"  OF  METAL 


Since  the  advent  of  chemistry  in  foundry  practice  there 
is  no  metallurgical  invention  that  has  proved  so  useful  as 
the  thermit  process  as  perfected  by  Dr.  Hans  Goldschmidt. 
Its  flexibility  and  simplicity  appeal  strongly  to  the  steel 
foundrymen  for  supplying  liquid  steel  in  almost  any  quan- 
tity quickly  and  at  any  time.  The  process  has  been  too 
well  promulgated  in  the  technical  press  to  need  any  ex- 
planation here  as  to  its  composition  and  action.  Rather 
the  remarks  herein  will  relate  to  the  methods  of  applying 
it  in  the  practice  of  making  repairs  of  the  defects  com- 
mon to  steel  castings.  The  consideration  from  the  foundry 
standpoint  is  mainly  appearance  and  in  this  regard  ther- 
mit is  superior  to  all  means,  in  the  writer's  knowledge  and 
experience,  of  remedying  unsightly  flaws  which  can  cause 
rejection  without  depreciating  the  strength. 

Whether  a  casting  should  or  should  not  be  repaired 
with  thermit  will  depend  upon  the  cost  of  the  operation.  If 
the  repair  cost  should  exceed  the  molding  cost,  it  will  be 
cheaper  to  re-melt  it,  because  the  casting  will  always  have 
a  credit  value  on  the  basis  of  the  market  price  of  scrap 
and  the  loss  because  of  the  flaw  will  only  represent  the 
labor  in  molding  and  handling.  The  question  of  delivery 
frequently  offsets  other  considerations. 

Many  castings  are  of  such  a  size  that  they  can  be  readily 


112  REPAIR  OF  CASTINGS  WITH  THERMIT 


repaired  in  blacksmith's  fire  at  a  nominal  cost  for  fuel  and 
labor.  Thermit  is  extremely  useful  in  heavy,  valuable 
castings.  The  commonest  flaws  in  them  are  shrink-holes, 
under-headers,  sand-holes,  miss-runs  and  cracks. 

If  the  defect  is  a  shrink-hole  or  sand-hole  and  where 
there  is  no  machined  surface,  the  method  of  filling  is  quite 
simple.  There  may  be  some  grease  or  oil  in  the  hole 
which  must  be  removed  before  it  can  be  welded.  It  is  not 
always  possible  to  pre-heat  or  burn  out,  because  the  oper- 
ation is  slow  and  tedious,  particularly  in  the  case  of  large 
castings,  and  there  may  not  be  a  large  torch  or  oil  burner 
convenient.  The  simplest  way  to  remove  the  grease  is  to 
pour  into  the  hole  some  lose  thermit,  ignite  it  and  allow 
the  heat  of  the  reaction  to  burn  out  the  oil,  grease  and  dirt 
which  it  will  do  most  effectively.  There  will  be  a  violent 
sputtering  in  the  hole  and  a  mass  of  slag  and  spongy  metal. 
The  slag  can  be  chipped  out  readily.  The  hole  is  then 
ready  for  the  final  treatment.  A  gate-pin  can  be  secured 
which  must  be  larger  in  diameter  by  at  least  I  inch  than 
the  hole.  It  should  be  placed  over  it  in  an  upright  position, 
and  some  green  molding  sand  packed  around  it.  With- 
drawing the  pin  leaves  a  mold  into  which  the  thermit  can 
be  placed.  The  depth  of  the  mold  should  be  at  least  2^ 
inches.  When  the  thermit  is  ignited,  and  while  burning, 
some  loose  thermit  should  be  poured  upon  it  for  the  reason 
that  the  mold  will  not  hold  in  the  first  instance  enough 
thermit  to  completely  fill  the  hole.  As  soon  as  the  action 
has  ceased  and  the  slag  solidified  the  mold  can  be  broken 
away  together  with  the  mass  of  slag.  The  button  of  metal 
will  be  white  hot  and  as  soon  as  it  reaches  a  yellow  or 
bright  red  it  can  be  forged  by  a  hand  hammer.  This 
treatment  will  effectively  and  cheaply  fill  any  hole  of  the 
character  described  on  surfaces  that  will  not  require  ma- 
chining. The  button  of  metal  will  protrude  more  or  less, 
but  it  can  be  ground  down  or  chipped,  preferably  ground. 

In  case  such  defects  as  just  mentioned  are  on  surfaces 
that  may  require  machining,  a  different  procedure  is  neces- 


REPAIR  OF  CASTINGS  WITH   THERMIT 


sary  because  blow-holes  must  be  absent  from  such  sur- 
faces. The  same  method  of  removing  grease  and  dirt  can 
be  followed  as  in  the  foregoing  paragraph  and  a  charcoal 
or  coke  fire  can  be  built  over  the  flaw.  Sand  must  be  re- 
moved by  chipping  to  expose  clean  metal.  The  mold  must 
be  dry  sand.  It  can  be  made  from  a  slab-core  by  cutting 
a  recess  or  hole  in  it  with  a  file.  The  mold  must  be  as  large 
in  diameter  inside  in  excess  of  diameter  of  the  flaw,  as  in 
the  previously  described  method,  and  must  be  carefully 
placed  over  the  flaw,  weighed  down  and  the  joints  daubed 
with  moist  clay  or  dough  and  backed  by  green  sand.  A 
thermit  crucible  is  then  placed  directly  over  the  mold, 
charged,  ignited  and  tapped  in  the  usual  manner.  It  is  not 
recommended  in  this  case  to  attempt  to  forge  or  hammer 
the  button  while  hot.  Let  the  parts  cool  down  normally. 
Afterwards  grind  the  button  down  flush.  Grinding  is  bet- 
ter than  tooling  because  the  button,  if  the  proper  quantity 
of  thermit  has  been  used,  will  stand  up  some  distance  when 
the  casting  is  placed  upon  a  planer,  and  if  the  leverage  of 
the  tool  is  too  great  and  there  is  danger  of  taking  too  heavy 
a  cut,  thus  tearing  the  soft  thermit  metal  out.  Because  of 
its  softness  it  gathers  under  or  crowds  the  tool  and  also 
prevents  or  interferes  with  free  cutting,  increasing  the  re- 
sistance and  danger  of  tearing.  A  light  cut  can  be  taken 
and  when  the  button  decreases  in  size,  of  course  the  lever- 
age decreases,  too.  Should  the  metal  be  porous  from  any 
cause,  or  should  the  weld  be  imperfect  because  of  an  in- 
sufficiency of  thermit  in  the  first  instance  for  welding,  the 
operation  can  be  repeated  since  thermit  metal  welds  beau- 
tifully to  the  same  metal  and  a  second  treatment  usually 
satisfactorily  finishes  the  job. 

In  case  of  shrinkage  cracks,  the  metal  must  be  cut  away 
along  the  line  of  the  opening  to  the  extent  of  at  least  J4 
inch  or  more.  A  mold  of  core  material  must  be  rammed 
on  the  casting  to  get  the  contour  of  the  parts,  allowing  a 
mold  space  to  form  a  band  overlapping  the  edges  of  the 
opening  at  least  ^  inch  on  each  side  of  it  and  from  24  to 


114  REPAIR  OF  CASTINGS  WITH  THERMIT 


I  inch  in  thickness.  In  welding  such  flaws  the  incoming 
thermit  metal  must  enter  the  mold  at  the  lowest  point  and 
overflow  at  the  highest,  using  enough  to  get  a  good  circu- 
lation. When  cool  the  band  of  metal  can  be  removed  to 
the  finished  surface. 

No  fixed  rule  can  be  laid  down  as  to  the  quantity  of 
thermit  to  use.  Usually  there  are  no  scales  in  the  cleaning 
room  of  a  steel  foundry,  and  the  operator  must  use  his 
own  judgment  how  much  to  use  for  a  given  operation. 
Practice  alone  will  govern  and  there  is  always  the  satisfac- 
tion of  knowing  that  if  a  weld  be  imperfect  from  any  cause 
it  can  be  repeated. 

All  foundrymen  are  familiar  with  the  well  known  "burn- 
ing-on"  of  metal.  Thermit  practice  is  essentially  in  many 
details  the  same  operation  with  the  advantage  that  a  "burn" 
can  be  made  at  any  convenient  time  if  the  compound  is 
available.  The  same  rules  will  apply  as  in  "burning-on"  ex- 
cepting that  allowance  must  be  made  for  a  voluminous 
slag  which  always  accompanies  an  action  of  thermit. 

The  operation  of  "burning-on"  by  ordinary  liquid  steel 
can  be  augmented  by  adding  thermit  to  the  ladle  of  steel 
taken  for  the  purpose.  An  addition  of  5  per  cent  by  weight 
will  greatly  increase  the  temperature  of  the  steel  and  of 
course  make  the  operation  sure  because  of  the  gain  in  heat. 


CHAPTER  XII 


COST  OF  EQUIPPING  FOUNDRIES  FOR  THE  MANUFACTURE 
OF  OPEN-HEARTH  STEEL  CASTINGS — STEEL  DEPART- 
MENT FOR  GRAY  IRON  FOUNDRIES — ESTIMATED 
PROFITS 

Owing  to  the  widespread  interest  manifested  in  the 
erection  of  steel  casting  plants  there  has  been  considerable 
speculation  as  to  the  cost  of  their  equipment.  The  follow- 
ing estimate  is  made  on  ,the  basis  of  daily  output  of  sound 
and  salable  castings,  per  ton  of  capacity: 

Furnaces  only  $1,200 

Gas  producers  and  gas  mains,  or  oil  storage  tanks  and 

accessories  600 

Buildings,  800  square  feet  of  floor  space  per  ton,  at 

$1.25  per  foot 1,000 

Power,  machinery,  cranes,  hoists,  molding  machines', 

tools,  drying  ovens,  etc 2,300 


Total  cost  per  ton   $5,100 

These  figures  are  based  on  a  plant  having  an  estimated 
capacity  of  150  to  160  tons  per  day,  or  4,000  tons  monthly, 
with  an  equipment  of  5  open-hearth  furnaces  costing  ap- 
proximately $750,000.  A  single  open-hearth  furnace 
lined  for  acid  melting  costs  very  nearly  $1,000  per  ton  ca- 
pacity. One  for  basic  melting  costs  $1,200  per  ton  capac- 
ity. These  figures  cover  excavation,  brick  work,  castings 


Il6  COST  OF  EQUIPMENT 


and  structural  material,  including  stack,  but  do  not  cover 
the  platform  or  facilities  for  charging. 

STEEL  DEPARTMENT  FOR  GRAY  IRON   FOUNDRIES 

The  average  capacity  of  a  furnace  for  open-hearth  steel 
casting  work  is  20  tons.  The  number  of  furnaces  in  oper- 
ation in  a  given  shop  with  two  or  more  furnaces  will  vary 
according  to  the  demand.  When  castings  are  the  only 
product,  at  least  one  furnace  should  be  kept  in  reserve, 
pending  repairs  or  a  shut-down  in  the  active  furnaces. 
This  will  equalize  deliveries  and  production.  Gray  iron 
foundries  using  steel  castings  will  undoubtedly  find  it 
profitable  to  install  an  open-hearth  furnace  which  should 
be  of  a  size  that  can  conveniently  fit  in  with  the  existing 
equipment  for  handling  ladles  of  hot  metal.  Would  recom- 
mend a  basic  lining,  since  it  permits  the  purchase  of  cheap 
iron  and  almost  any  kind  of  steel  scrap.  The  basic  process 
has  reached  such  a  stage  of  development  that  any  foundry- 
man  with  intelligence  can  successfully  acquire  the  skill  for 
its  profitable  operation.  Modern  foundry  chemistry  is  fatal 
to  mysterious  information.  There  are  no  secrets  or  esote- 
ric systems  known  only  to  the  few.  The  principles  of  basic 
practice  are  an  open  book. 

With  a  basic  furnace  in  an  active  gray  iron  foundry  of 
anything  like  a  modern  character  it  would  be  perfectly 
feasible  to  manufacture  steel  castings  in  moderate,  profit- 
able quantities  in  conjunction  with  the  regular  product. 
About  the  only  change  necessary  in  the  molding  end  of  the 
practice  would  be  a  supply  of  silica  sand  and  a  sand  mill 
to  prepare  the  molding  mixtures.  A  furnace  of  convenient 
size  would  have  a  capacity  of  5  tons  per  heat.  Such  a  fur- 
nace could  easily  produce  four  heats  in  24  hours  and  could 
be  depended  upon  to  regularly  make  at  least  three,  and  if 
desired,  only  one  heat  per  day.  In  the  meantime,  however, 
there  would  be  a  steady  consumption  of  fuel  to  keep  the 
furnace  hot.  The  fuel  should  be  either  natural  gas  or  fuel 


COST  OF  EQUIPMENT  1 17 


oil.  Producer  gas  is  often  uncertain,  irregular  in  com- 
position, and  requires  additional  labor  for  attendance  and 
maintenance. 


COST  OF  A  FIVE-TON  FURNACE 

A  5-ton  basic  open-hearth  furnace  would  cost  approxi- 
mately $6,000  if  erected  in  a  modern  active  iron  foundry. 
As  an  additional  outlay  to  cover  bottom  pour  ladles,  fur- 
nace platform,  oil  storage  tanks,  pumps,  oil  piping,  burn- 
ers, etc.,  a  liberal  figure  would  be  $4,000,  making  a  total 
expenditure  of  $10,000,  not  including,  however,  the  build- 
ings. 

Charging  5  tons  per  heat,  consisting  of  50  per  cent  pig 
iron  and  50  per  cent  scrap,  there  should  be  produced  under 
normal  practice,  12^  tons  daily  at  the  rate  of  three  heats 
in  24  hours.  The  loss  or  shrinkage  is  estimated  at  15  per 
cent  which  includes  the  melting  loss,  gates,  risers,  sculls 
and  defective  castings.  The  melting  loss  in  the  furnace  is, 
on  the  average,  7  per  cent.  This  low  loss  is  an  important 
economical  factor. 


PROFITABLE    INVESTMENT 

With  a  normal  demand  for  castings  an  average  profit  of 
YT.  per  cent  per  pound  could  be  expected,  or  $10  per  net 
ton  of  product,  which  would  be  equivalent  to  $127.50  per 
day.  There  would  be  times  when  the  furnace  would  be  out 
of  commission  for  repairs,  periods  which  should  not  exceed 
one  month  at  the  most,  but  under  ordinary  conditions  two 
weeks  should  cover  general  overhauling.  With  proper 
care  a  basic  furnace  is  capable  of  producing  400  heats  be- 
fore undergoing  general  repairs,  or  a  campaign  of  133 
working  days,  in  round  numbers  four  months.  Assuming 
the  active  period  for  production  would  only  be  nine  months 
in  the  year  at  the  rate  of  25  working  days  per 


Il8  COST   OF   EQUIPMENT 


month,  there  would  be  a  productive  period  of  225 
working  days.  At  the  rate  of  12^4  tons  per 
day  or  a  yearly  total  of  2,868^4  tons  at  $10  per 
ton,  would  yield  a  profit  of  $28,687.50,  figures  which 
look  attractive  from  a  promoter's  view  point,  and  might  be 
vivid  to  embody  in  a  prospectus.  But,  there  would  be 
times  when  the  yield  would  shrink  considerably,  owing  to 
errors  in  practice,  break-downs,  delays  and  other  detrac- 
tive conditions,  which  would  seriously  decrease  the  dif- 
ference between  manufacturing  costs  and  selling  prices. 
As  an  extreme  case,  it  will  be  assumed  that  the  yield  over 
metal  charged  was  only  50  per  cent  good  castings  for  the 
entire  productive  period  as  estimated;  that  the  average 
profit  was  decreased  to  3^  cent  per  pound  and  that  the  ton- 
nage was  only  7^  tons  daily  or  1,687^  tons  yearly.  The 
profit  then  would  be  $4,218.75,  and  charging  off  25  per 
cent  for  interest,  replacements,  depreciation,  etc.,  there 
would  be  a  net  return  of  $3,164.07  on  an  investment  of 
$10,000  for  a  five- ton  furnace  in  an  active  iron  foundry. 
This  would  be  equivalent  to  a  profit  of  31  6-10  per  cent  on 
the  outlay,  which,  in  view  of  the  extremely  unfavorable 
conditions  considered  in  the  estimating,  makes  a  steel  foun- 
dry as  profitable  as  any  foundry  enterprise. 

An  open-hearth  steel  foundry,  with  intelligent  practice 
and  normal  times  or  demand,  offers  an  attractive  venture 
to  the  investor  and  no  doubt  will  receive  the  attention  of 
gray  iron  founders  who  are  interested  in  steel  casting 
manufacture. 


UNIVERSITY 

OF 


. 

Tare  BOOR 


^ 


MAR     2   1933 


29  J948 


2Jun$3KH 


,6Ja'59ES| 

ct> 

JAU   21959 


